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Archive of Mathematica weekly newsletters

Nasser M. Abbasi

September 20, 2017 compiled on — Wednesday September 20, 2017 at 12:45 PM [public]

Contents

1 Tuesday, September 19, 2017
2 Tuesday, September 12, 2017
3 Tuesday, September 5, 2017
4 Tuesday, August 29, 2017
5 Tuesday, August 22, 2017
6 Tuesday, August 15, 2017
7 Tuesday, August 8, 2017
8 Tuesday, August 1, 2017
9 Tuesday, July 25, 2017
10 Tuesday, July 18, 2017
11 Tuesday, July 11, 2017
12 Tuesday, July 4, 2017
13 Tuesday, June 27, 2017
14 Tuesday, June 20, 2017
15 Tuesday, June 13, 2017
16 Tuesday, June 6, 2017
17 Tuesday, May 30, 2017
18 Tuesday, May 23, 2017
19 Tuesday, May 16, 2017
20 Tuesday, May 2, 2017
21 Tuesday, April 25, 2017
22 Tuesday, April 18, 2017
23 Tuesday, April 11, 2017
24 Tuesday, April 4, 2017
25 Tuesday, March 28, 2017
26 Tuesday, March 21, 2017
27 Tuesday, March 14, 2017
28 Tuesday, March 7, 2017
29 Tuesday, February 28, 2017
30 Tuesday, February 21, 2017
31 Tuesday, February 14, 2017
32 Tuesday, February 7, 2017
33 Tuesday, January 31, 2017
34 Tuesday, January 24, 2017
35 Tuesday, January 17, 2017
36 Tuesday, January 10, 2017
37 Tuesday, January 3, 2017
38 Tuesday, December 27, 2016
39 Tuesday, December 20, 2016
40 Tuesday, December 13, 2016
41 Tuesday, December 6, 2016
42 Tuesday, November 29, 2016
43 Tuesday, November 22, 2016
44 Tuesday, November 15, 2016
45 Tuesday, November 8, 2016
46 Tuesday, November 1, 2016
47 Tuesday, October 25, 2016
48 Tuesday, October 18, 2016
49 Tuesday, October 11, 2016
50 Tuesday, October 4, 2016
51 Tuesday, September 27, 2016
52 Tuesday, September 20, 2016
53 Tuesday, September 13, 2016
54 Tuesday, September 6, 2016
55 Tuesday, August 30, 2016
56 Tuesday, August 23, 2016
57 Tuesday, August 16, 2016
58 Tuesday, August 9, 2016
59 Tuesday, August 2, 2016
60 Tuesday, July 26, 2016
61 Tuesday, July 19, 2016
62 Tuesday, July 12, 2016
63 Tuesday, July 5, 2016
64 Tuesday, June 28, 2016
65 Tuesday, June 21, 2016
66 Tuesday, June 14, 2016
67 Tuesday, June 7, 2016
68 Tuesday, May 31, 2016
69 Tuesday, May 24, 2016
70 Tuesday, May 17, 2016
71 Tuesday, May 10, 2016
72 Tuesday, May 3, 2016
73 Tuesday, April 26, 2016
74 Tuesday, April 19, 2016
75 Tuesday, April 12, 2016
76 Tuesday, April 5, 2016
77 Tuesday, March 29, 2016
78 Tuesday, March 22, 2016
79 Tuesday, March 15, 2016
80 Tuesday, March 8, 2016
81 Tuesday, March 1, 2016
82 Tuesday, February 23, 2016
83 Tuesday, February 16, 2016
84 Tuesday, February 9, 2016
85 Tuesday, February 2, 2016
86 Tuesday, January 26, 2016
87 Tuesday, January 19, 2016
88 Tuesday, January 12, 2016
89 Tuesday, January 5, 2016
90 Tuesday, December 29, 2015
91 Tuesday, December 22, 2015
92 Tuesday, December 15, 2015
93 Tuesday, December 8, 2015
94 Tuesday, December 1, 2015
95 Tuesday, November 24, 2015
96 Tuesday, November 17, 2015
97 Tuesday, November 10, 2015
98 Tuesday, November 3, 2015
99 Tuesday, October 27, 2015
100 Tuesday, October 20, 2015
101 Tuesday, October 13, 2015
102 Tuesday, October 6, 2015
103 Tuesday, September 29, 2015
104 Tuesday, September 22, 2015
105 Tuesday, September 15, 2015
106 Tuesday, September 8, 2015
107 Tuesday, September 1, 2015
108 Tuesday, August 25, 2015
109 Tuesday, August 18, 2015
110 Tuesday, August 11, 2015
111 Tuesday, August 4, 2015
112 Tuesday, July 28, 2015
113 Tuesday, July 21, 2015
114 Tuesday, July 14, 2015
115 Tuesday, July 7, 2015
116 Tuesday, June 30, 2015
117 Tuesday, June 23, 2015
118 Tuesday, June 16, 2015
119 Tuesday, June 9, 2015
120 Tuesday, June 2, 2015
121 Tuesday, May 26, 2015
122 Tuesday, May 19, 2015
123 Tuesday, May 12, 2015
124 Tuesday, May 5, 2015
125 Tuesday, April 28, 2015
126 Tuesday, April 21, 2015
127 Tuesday, April 14, 2015
128 Tuesday, April 7, 2015
129 Tuesday, March 31, 2015
130 Tuesday, March 24, 2015
131 Tuesday, March 17, 2015
132 Tuesday, March 10, 2015
133 Tuesday, March 3, 2015
134 Tuesday, February 17, 2015
135 Tuesday, February 17, 2015
136 Tuesday, February 10, 2015
137 Tuesday, February 3, 2015
138 Tuesday, January 27, 2015
139 Tuesday, January 20, 2015
140 Tuesday, January 13, 2015
141 Tuesday, January 6, 2015
142 Tuesday, December 30, 2014
143 Tuesday, December 16, 2014
144 Tuesday, December 16, 2014
145 Tuesday, December 9, 2014
146 Tuesday, December 2, 2014
147 Tuesday, November 25, 2014
148 Tuesday, November 18, 2014
149 Tuesday, November 11, 2014
150 Tuesday, November 4, 2014
151 Tuesday, October 28, 2014
152 Tuesday, October 21, 2014
153 Tuesday, October 14, 2014
154 Tuesday, October 7, 2014
155 Tuesday, September 30, 2014
156 Tuesday, September 23, 2014
157 Tuesday, September 16, 2014
158 Tuesday, September 9, 2014
159 September 2, 2014
160 August 26, 2014
161 August 19, 2014
162 August 12, 2014
163 August 5, 2014
164 July 29, 2014
165 July 22, 2014
166 July 15, 2014
167 July 8,2014
168 July 1, 2014
169 June 24, 2014
170 June 17, 2014
171 June 10, 2014
172 June 3, 2014
173 May 27 2014
174 May 20 2014
175 May 13, 2014
176 May 6, 2014
177 April 15, 2014
178 April 1, 2014
179 March 25, 2014
180 March 18, 2014
181 March 11, 2014
182 March 4, 2014
183 February 25, 2014
184 February 18, 2014
185 February 11, 2014
186 February 4, 2014
187 January 28, 2014
188 January 21, 2014
189 January 14, 2014
190 January 7, 2014
191 December 31, 2013
192 December 24, 2013
193 December 17, 2014
194 December 10, 2013
195 December 3, 2013
196 November 26, 2013
197 November 19, 2013
198 November 12, 2013
199 November 5, 2013
200 October 29, 2013
201 October 22, 2013
202 October 15, 2013
203 October 1, 2013
204 September 24, 2013
205 September 17, 2013
206 September 10, 2013
207 September 3, 2013
208 August 27, 2013
209 August 20, 2013
210 April 29, 2013
211 April 22, 2013
212 April 8, 2013

1 Tuesday, September 19, 2017

==================================
Top new questions this week:
==================================

[Pop-up appeared and then disappeared during first documentation search in 11.2] https://mathematica.stackexchange.com/questions/155717/pop-up-appeared-and-then-disappeared-during-first-documentation-search-in-11-2

After installing Mathematica 11.2, the first time I searched for something in the help center a pop-up appeared and then disappeared. It didn’t appear on a subsequent search, even if I restarted ...

- asked by Itai Seggev (23 votes), answered by Itai Seggev (26 votes)

—————————-

[ExternalEvaluate for Python fails with Import::nopythonevals] https://mathematica.stackexchange.com/questions/155821/externalevaluate-for-python-fails-with-importnopythonevals

I tried using ExternalEvaluate on OS X with Anaconda Python, and every ExternalEvaluate call failed with the Import::nopythonevals message. This happened even though an external evaluator was ...

- asked by Szabolcs (15 votes), answered by Szabolcs (12 votes)

—————————-

[Visualizing a holomorphic bijection between the unit disc and a domain] https://mathematica.stackexchange.com/questions/155954/visualizing-a-holomorphic-bijection-between-the-unit-disc-and-a-domain

One can construct a holomorphic bijection between the (open) unit disc D = {z ∈ C : |z| < 1} , and a domain    -----------
D ∖B1 ∕2(− 1∕2)  where Br(z0)  denotes the ball of radius r  ...

- asked by Jack (12 votes), answered by Michael E2 (13 votes)

—————————-

[How to create search indices for custom documentation pages?] https://mathematica.stackexchange.com/questions/155932/how-to-create-search-indices-for-custom-documentation-pages

I have a package that uses custom documentation pages that are not generated with Wolfram Workbench.

How can I create search indices for these pages?

Requirements:

Searching should work in ...

- asked by Szabolcs (10 votes), answered by Szabolcs (1 vote)

—————————-

[Compile M11.1-compatible LibraryLink libraries using M11.2] https://mathematica.stackexchange.com/questions/155940/compile-m11-1-compatible-librarylink-libraries-using-m11-2

WolframLibraryVersion, defined in WolframLibrary.h, was bumped from 3 to 4 in Mathematica 11.2. This causes libraries compiled with M11.2 to fail to load in earlier versions.

Is it possible to ...

- asked by Szabolcs (9 votes)

—————————-

[How to insert dimensions in graphics?] https://mathematica.stackexchange.com/questions/155677/how-to-insert-dimensions-in-graphics

I’m creating figures (a T beam section) using the Graphics function. Like this:

a = Graphics[Polygon[{{0, 80}, {0, 85}, {100, 85}, {100, 80}}]];
b = Graphics[Polygon[{{47.5, 80}, {52.5, 80}, {52.5,  ...

- asked by Diogo (9 votes), answered by wxffles (10 votes)

—————————-

[Mathematica 11.2 Import Statement Produces Errors & Truncates CSV Data Created in 11.1] https://mathematica.stackexchange.com/questions/155908/mathematica-11-2-import-statement-produces-errors-truncates-csv-data-created-i

Bug introduced in 11.2.0

TL;DR


Issue 1 (bug): Import of CSV files with column specification fails
when "HeaderLines" or "SkipLines" option is used:

Import["ExampleData/financialtimeseries.csv",  ...

- asked by Joseph Karpinski (8 votes), answered by Itai Seggev (8 votes)

================================== Greatest hits from previous weeks: ==================================

[How to tell Mathematica that certain variables are real/imaginary, integer-valued, etc] https://mathematica.stackexchange.com/questions/66273/how-to-tell-mathematica-that-certain-variables-are-real-imaginary-integer-value

I’m trying to expedite some quantum mechanical calculations (expectation values etc.) by running them through Mathematica. When I say, for example,

u[x_] := Sqrt[2/L] * Sin[Pi * n * x / L]

and then ...

- asked by Matthew Brunetti (17 votes), answered by SquareOne (11 votes)

—————————-

[How do I clear all user defined symbols?] https://mathematica.stackexchange.com/questions/850/how-do-i-clear-all-user-defined-symbols

Is there some way to do this other than going to Evaluation -&gt; Quit
kernel and firing a new one up?

- asked by niklasfi (55 votes), answered by Artes (54 votes)

================================== Can you answer these? ==================================

[Covariant derivative given Christoffel symbols] https://mathematica.stackexchange.com/questions/155871/covariant-derivative-given-christoffel-symbols

I’ve been trying to take covariant derivative of various quantities along various surfaces in Mathematica, but I keep running into issues, frequently I get a tensor with the wrong dimension. Using the ...

- asked by Noahb32 (1 vote)

—————————-

[How to pass in-memory images through ExternalEvaluate?] https://mathematica.stackexchange.com/questions/156051/how-to-pass-in-memory-images-through-externalevaluate

Version 11.2 has a new import/export format PythonExpression.

Unfortunately, it doesn’t work out-of-the-box with images:

And using the ImageData directly is too slow:

Anyhow, I have some image ...

- asked by M.R. (4 votes)

—————————-

[GeneralizedLinearModelFit IRwLS] https://mathematica.stackexchange.com/questions/155692/generalizedlinearmodelfit-irwls

I’m interested in Mathematica’s capabilities with regard to robust fitting vs. outliers. In the Statistical Model Analysis Tutorial under the Generalized Linear Models section heading, there is this ...

- asked by Chris Chiasson (1 vote)

2 Tuesday, September 12, 2017

==================================
Top new questions this week:
==================================

[Framework behind Graph plots. DynamicNamespace and friends] https://mathematica.stackexchange.com/questions/155237/framework-behind-graph-plots-dynamicnamespace-and-friends

As shown in DynamicLocation usage, we can use it to quickly create very nice functionality, that it to refer to graphics’ primitives relative coordinates without calculations of boundary etc.

As ...

- asked by Kuba (15 votes), answered by Kuba (12 votes)

—————————-

[DynamicLocation usage] https://mathematica.stackexchange.com/questions/155157/dynamiclocation-usage

Background

DynamicLocation can be very useful:

LocatorPane[Dynamic@x,
  Graphics[
    { EdgeForm @ Thick, FaceForm @ None, Rectangle[BoxID -&gt; "box"]
    , Arrow[{Dynamic[x],  ...

- asked by Kuba (14 votes), answered by b3m2a1 (9 votes)

—————————-

[How can I use GitHub as a paclet server?] https://mathematica.stackexchange.com/questions/155123/how-can-i-use-github-as-a-paclet-server

I want to use GitHub as a paclet server, but this fails:

PacletInstall[
 "ServiceConnection_StackExchange",
 "Site" -&gt; "https:/github.com/b3m2a1/PacletServer"
 ]

PacletSiteUpdate::err: An error  ...

- asked by b3m2a1 (13 votes), answered by b3m2a1 (16 votes)

—————————-

[Permanently extending the behaviour of functions (like decorators)] https://mathematica.stackexchange.com/questions/155567/permanently-extending-the-behaviour-of-functions-like-decorators

Suppose I have a function, e.g.

f[x_] := x^2


It works like this:

f[5]
(* 25 *)

I would like to permanently modify it so that calling f[5] will perform some action before and after the evaluation ...

- asked by Szabolcs (11 votes), answered by Leonid Shifrin (9 votes)

—————————-

[Is Tooltip broken in MMA 11.1.1?] https://mathematica.stackexchange.com/questions/155434/is-tooltip-broken-in-mma-11-1-1

Bug introduced in 11.1.0 and persisting through 11.1.1

I have just discovered that Tooltip works differently from as described in the documentation, at least in my version of MMA (11.1.1.0, Windows ...

- asked by Oleg Soloviev (9 votes)

—————————-

[Install paclets into $BaseDirectory on multi-user system] https://mathematica.stackexchange.com/questions/155122/install-paclets-into-basedirectory-on-multi-user-system

PacletInstall will install paclets into the $UserBaseDirectory by default. How can we install them in $BaseDirectory so that all users on the system will have access? Is this currently possible?

...

- asked by Szabolcs (9 votes), answered by halirutan (5 votes)

—————————-

[How can I reproduce the result of PrincipalComponents] https://mathematica.stackexchange.com/questions/155467/how-can-i-reproduce-the-result-of-principalcomponents

matrix = N[{{1, 2}, {2, 3}, {4, 10}}]
   {{1., 2.}, {2., 3.}, {4., 10.}}

res1 = PrincipalComponents[matrix, Method -&gt; "Correlation"]
   {{1.10388, 0.130549}, {0.478746, -0.170139}, {-1.58262,  ...

- asked by HyperGroups (8 votes), answered by J. M. (13 votes)

================================== Greatest hits from previous weeks: ==================================

[Labeling individual curves in Mathematica] https://mathematica.stackexchange.com/questions/4444/labeling-individual-curves-in-mathematica

I need to create a plot for export and inclusion in a report. Is there a better way to label curves than PlotLegends? From what I’ve read and my personal experience, PlotLegends is pretty bad.

Is ...

- asked by Tianxiang Xiong (52 votes), answered by Artes (40 votes)

—————————-

[What does # mean in Mathematica?] https://mathematica.stackexchange.com/questions/19035/what-does-mean-in-mathematica

I asked Mathematica to compute the following

Solve[c (1-x)^2-x^(1/4) == 0, x]

and it returned this:

  x = Root[#1^8 c^4 - 8 #1^7 c^4 + 28 #1^6 c^4 - 56 #1^5 c^4 + 70 #1^4 c^4 - 56 #1^3 c^4 + 28  ...

- asked by ronanymous (20 votes), answered by Dr. belisarius (43 votes)

================================== Can you answer these? ==================================

[Question about RandomSeed option in AdaptiveMonteCarlo NIntegrate method] https://mathematica.stackexchange.com/questions/155249/question-about-randomseed-option-in-adaptivemontecarlo-nintegrate-method

I’ve been familiarising myself with the different options available in the AdaptiveMonteCarlo method for NIntegrate but one of the things that I can’t really understand is what the numbers correspond ...

- asked by user35305 (1 vote)

—————————-

[Delete duplicates in a list compiled of different lists and also delete] https://mathematica.stackexchange.com/questions/155261/delete-duplicates-in-a-list-compiled-of-different-lists-and-also-delete

Ive got three lists: Lst1 has 100 different values for "r".
Lst2 has 100 different values for "a". And Lst3=Pi*Lst1^2*Lst2.
In Lst3 Ive got duplicates and I want to get rid of them, but I also want  ...

- asked by Cornelis (1 vote)

—————————-

[How to implement LinkLaunch-like functionality with timeout?] https://mathematica.stackexchange.com/questions/155493/how-to-implement-linklaunch-like-functionality-with-timeout

tl;dr: What is the best way (and correct sequence of operations) to connect two programs using MathLink while anticipating failures / timeouts?

Launch program and connect, with timeout

I have a ...

- asked by Szabolcs (4 votes)

3 Tuesday, September 5, 2017

==================================
Top new questions this week:
==================================

[Finding nth   largest/smallest element] https://mathematica.stackexchange.com/questions/154944/finding-n-textth-largest-smallest-element

Ordering can quickly find the position of the largest/smallest element in a list, but finding the position of the  th
n   largest/smallest element is much slower:

data = RandomReal[10, 10^7];

...

- asked by Carl Woll (13 votes), answered by Carl Woll (12 votes)

—————————-

[Fast pairwise SameQ test of an ordered list] https://mathematica.stackexchange.com/questions/155017/fast-pairwise-sameq-test-of-an-ordered-list

I have an ordered list of N  numbers, and I want to find out whether adjacent numbers are SameQ or not, returning a list of 0s and 1s of length N −  1  . One approach is something like:

...

- asked by Carl Woll (11 votes), answered by jkuczm (8 votes)

—————————-

[Given an ordered set S, find the points in S corresponding to another list] https://mathematica.stackexchange.com/questions/154893/given-an-ordered-set-s-find-the-points-in-s-corresponding-to-another-list

Given a sorted list of numbers S  , I want to create a function that accepts a list of numbers L  and for each number l ∈ L  it returns the index of the largest number s ∈ S  such that ...

- asked by Carl Woll (11 votes), answered by nikie (13 votes)

—————————-

[Geolocate multiple IP addresses] https://mathematica.stackexchange.com/questions/155076/geolocate-multiple-ip-addresses

I would like to geolocate a few hundred IP addresses (as part of analysing server logs). What is the best way to do this using Mathematica?

Does Mathematica have any builtin functionality for this?

...

- asked by Szabolcs (9 votes), answered by Szabolcs (9 votes)

—————————-

[How to connect two images] https://mathematica.stackexchange.com/questions/155093/how-to-connect-two-images

I have talk about how to catenate two images whose have same part totally in my this post.

But in this case two images have similar information, not totally same.

img1 = Import @  ...

- asked by yode (9 votes), answered by Kuba (8 votes)

—————————-

[Filter elements in descending order] https://mathematica.stackexchange.com/questions/154761/filter-elements-in-descending-order

I want to solve the following problem efficiently:

Given a list of pairs (value, data), I want to remove all the pairs so that the resulting list has the value property of its elements sorted. That ...

- asked by José D. (9 votes), answered by Mathe172 (9 votes)

—————————-

[Changing numbers inside list to a list] https://mathematica.stackexchange.com/questions/154911/changing-numbers-inside-list-to-a-list

I have a list wich contains numbers and other lists, and what I want is to change every number x to x,0.

So if the function I’m seeking is called f, then

a = {1,Pi,2+3I,{1,2},{3,4},-2}


f[a]  ...

- asked by Garmekain (8 votes), answered by John Joseph M. Carrasco (10 votes)

================================== Greatest hits from previous weeks: ==================================

[Is it possible to draw this figure using Mathematica?] https://mathematica.stackexchange.com/questions/110848/is-it-possible-to-draw-this-figure-using-mathematica

The figure is

See the how-to video or a speeded-up GIF.

I believe it should be possible to draw this figure programmatically using some Random function, but I’m rather new to Mathematica, so I ...

- asked by AccidentalFourierTransform (62 votes), answered by M.R. (86 votes)

—————————-

[Can Mathematica do symbolic linear algebra?] https://mathematica.stackexchange.com/questions/3242/can-mathematica-do-symbolic-linear-algebra

For instance, is there some way I can say ”let A and B be arbitrary real m × n  and k × m  matrices, Simplify[Transpose[Transpose[A].Transpose[B]]]” and Mathematica would simplify it to B.A? ...

- asked by nikie (47 votes), answered by helen (25 votes)

================================== Can you answer these? ==================================

[Strange result for an improper integral ∫1  −1∕2    ( )
 0 xex−1-sin  1x dx  ] https://mathematica.stackexchange.com/questions/155066/strange-result-for-an-improper-integral-int-01-fracx-1-2ex-1-s

The improper integral

∫ 1  −1∕2    (  )
    x-----sin  1-  dx
 0  ex − 1     x
is convergent conditionally.

(Applying Dirichlet Test,

x −1∕2
ex-−-1
...

- asked by user250236 (1 vote)

—————————-

[Perplexing simplification of RotationMatrix] https://mathematica.stackexchange.com/questions/154793/perplexing-simplification-of-rotationmatrix

The result of

FullSimplify[RotationMatrix[θ, {Cos[ψ], Sin[ψ], 0}], ψ &gt; 0].{0, 0, 1}

in Mathematica 11 is

{Sign[Sec[ψ]]^2 Sin[θ] Sin[ψ], -Cos[ψ] Sin[θ], Cos[θ]}

instead of the nicer result ...

- asked by theindigamer (1 vote)

—————————-

[collecting terms with different order] https://mathematica.stackexchange.com/questions/154849/collecting-terms-with-different-order

I am using homotopy perturbation method to solve nonlinear ODE.

The first step is to introduce P parameter and collect different order of P.

The code is like this:

Collect[(1 -
 p) ((((1 +
        ...

- asked by sajad.sharhani (1 vote)

4 Tuesday, August 29, 2017

==================================
Top new questions this week:
==================================

[Inserting some zeros in a list by a rule of positions] https://mathematica.stackexchange.com/questions/154551/inserting-some-zeros-in-a-list-by-a-rule-of-positions

I have a list:

mainlist={0.23, 0.34, 0.8, 0.0, -0.2, 0.4, -0.1};

I have to extend the above list to another one finalresult with Length=17. But in finalresult the elements of the mainlist must be ...

- asked by Inzo Babaria (12 votes), answered by John Joseph M. Carrasco (14 votes)

—————————-

[How to use Streaming package in v11.1?] https://mathematica.stackexchange.com/questions/154439/how-to-use-streaming-package-in-v11-1

I am trying to use the streaming package for lazy list operations demonstrated in this post. But I found that the package was significantly changed in version 11. After some observations, I found that ...

- asked by happy fish (11 votes), answered by Leonid Shifrin (9 votes)

—————————-

[Interior of discretized region] https://mathematica.stackexchange.com/questions/154544/interior-of-discretized-region

I have some domain of interest:

r = 0.3;
dom = ImplicitRegion[(x - 1/2)^2 + (y - 1/2)^2 &gt;= r^2, {{x, 0, 1}, {y, 0, 1}}];

Now I can extract mesh of the whole domain or just boundary:

...

- asked by user16320 (9 votes), answered by C. E. (10 votes)

—————————-

[Orientation of boundary domain normals] https://mathematica.stackexchange.com/questions/154656/orientation-of-boundary-domain-normals

I would like to use BoundaryNormals provided by the ElementMesh object. To demonstrate my problem I will take my favorite domain:

dom = ImplicitRegion[(x - 1/2)^2 + (y - 1/2)^2 &gt;= (1/4)^2, {{x, 0,  ...

- asked by user16320 (8 votes), answered by user16320 (4 votes)

—————————-

[Best Practices for Creating CDF e-textbook] https://mathematica.stackexchange.com/questions/154550/best-practices-for-creating-cdf-e-textbook

I attended a talk given by Eric Schulz a few years ago. It was similar to his talk ”Sharing Wisdom Gained from Publishing a CDF Ebook” given here. I am Math instructor and have been creating ...

- asked by Michael McCain (8 votes)

—————————-

[Markdown parser in Mathematica] https://mathematica.stackexchange.com/questions/154634/markdown-parser-in-mathematica

Is there already a markdown to XML parser implemented in Mathematica? I wrote a one for my pelican rewrite, but realized I should have asked here first. Mine is almost certainly faulty in a few major ...

- asked by b3m2a1 (7 votes), answered by b3m2a1 (3 votes)

—————————-

[ListContourPlot with hatched regions] https://mathematica.stackexchange.com/questions/154481/listcontourplot-with-hatched-regions

I’m using ListContourPlot on a table of data, and I’d like to hash the regions rather than colour them, so the plot works in black and white.

data = Flatten[Table[{x, y, Cos[x] + Cos[y]}, {x, 0, 3,  ...

- asked by KraZug (7 votes), answered by John Joseph M. Carrasco (8 votes)

================================== Greatest hits from previous weeks: ==================================

[Creating legends for plots with multiple lines?] https://mathematica.stackexchange.com/questions/4025/creating-legends-for-plots-with-multiple-lines

So I have a graph with multiple lists, for e.g.

data = {{1,2}, {3,4}, {3,5}, {2,3} . . .}


If I then do ListLinePlot[Table[{#1,Log[b,#2]}&amp;@@@data, {b,1,10,2}]]
I have no way to generate a legend  ...

- asked by Eiyrioü von Kauyf (61 votes), answered by Jens (91 votes)

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[Learn Mathematica (Wolfram) Language in one day] https://mathematica.stackexchange.com/questions/138366/learn-mathematica-wolfram-language-in-one-day

Currently I am trying to learn Python. Searching for relevant material I came across

X in Y minutes

and books with titles such as Learn Python in one day, in 24 hours, etc.

Similar material exists ...

- asked by dimitris (26 votes), answered by masterxilo (11 votes)

================================== Can you answer these? ==================================

[NetTrain with External GPU?] https://mathematica.stackexchange.com/questions/154380/nettrain-with-external-gpu

I’d like to use the new Neural Networks functionalities in v11 on my Macbook Pro, unfortunately, most macs do not have the supported Nvidia cards. However, there is the option for using an external ...

- asked by M.R. (3 votes)

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[Solution (numerical or symbolic) of functional equations?] https://mathematica.stackexchange.com/questions/154515/solution-numerical-or-symbolic-of-functional-equations

Can I solve functional equations with Mathematica? How?

For example, I am trying to solve:

F(x)      ( (1+ x )2 )
F-(1)-= 2F   ---4a---  − F(x∕a)

for specific values of a  . Can ...

- asked by becko (1 vote)

—————————-

[Amplitude of a transfer function] https://mathematica.stackexchange.com/questions/154489/amplitude-of-a-transfer-function

I’m looking to calculate the amplitude of a transfer function which is defined in a symbolic way :

T=(1 + 2 I r λ)/(1 - r^2 + 2 I r λ)


I try this, i doesnt work

Assuming[{λ &gt; 0, r &gt; 0},  ...

- asked by Bendesarts (1 vote)

5 Tuesday, August 22, 2017

==================================
Top new questions this week:
==================================

[Mathematica vs. Comsol for finite element analysis?] https://mathematica.stackexchange.com/questions/154254/mathematica-vs-comsol-for-finite-element-analysis

Being relatively new to finite element analysis, I was wondering how expert users assess Mathematica’s capabilities in solving PDEs via the finite element method compared to other commercial tools ...

- asked by Alexander Erlich (13 votes), answered by Alexei Boulbitch (7 votes)

—————————-

[Mathematica Syntax Coloring in GitHub README] https://mathematica.stackexchange.com/questions/153836/mathematica-syntax-coloring-in-github-readme

GitHub doesn’t auto-detect and color Mathematica code in its markdown. Can we make it do so?

This may be trivial, but many README files don’t seem to have it.

- asked by b3m2a1 (10 votes), answered by b3m2a1 (13 votes)

—————————-

[HoldPattern vs Unevaluated] https://mathematica.stackexchange.com/questions/153844/holdpattern-vs-unevaluated

For learning purposes I created this code:

{g, 3*(10 + g)} /. HoldPattern[Plus[t__]] :&gt; (Plus[t] /. g -&gt; h)

I am learning about HoldPattern. As I understand it HoldPattern makes sure that the ...

- asked by GambitSquared (8 votes), answered by Mr.Wizard (9 votes)

—————————-

[Who is to blame: parsing UTF8 encoded JSON HTTPResponse fails] https://mathematica.stackexchange.com/questions/154245/who-is-to-blame-parsing-utf8-encoded-json-httpresponse-fails

Background

V11.1.1 I’m using URLRead to fetch some data,

can’t show everything but headers contain:

"content-type-&gt;application/json; charset=utf-8"

and body (returned from URLRead) contains ...

- asked by Kuba (7 votes), answered by Alexey Popkov (5 votes)

—————————-

[Number elements in a list] https://mathematica.stackexchange.com/questions/153951/number-elements-in-a-list

I’m trying to learn more about list replacement without using Table. I have a list like this:

list = {{{"a", "b", "c"}, {"d", "e", "f"}, {"g", "h", "i"}}}

Now, I want to modify the list elements, ...

- asked by holistic (7 votes), answered by MarcoB (9 votes)

—————————-

[Fill a sphere above an arbitrary curve] https://mathematica.stackexchange.com/questions/153994/fill-a-sphere-above-an-arbitrary-curve

I have a function which generates a curve on the surface of a unit sphere, parameterised by the azimuthal angle. How can I plot a sphere with two different colour above and below this curve?

f[t_] :=  ...

- asked by Tom (6 votes), answered by Kuba (9 votes)

—————————-

[is it possible to change/customize some conversions done by TeXForm?] https://mathematica.stackexchange.com/questions/153876/is-it-possible-to-change-customize-some-conversions-done-by-texform

I use TeXForm to convert output of some computation to Latex. I’d like to ask if there is a way to override/change/customize some of these conversions, related to just the name Mathematica assigns to ...

- asked by Nasser (6 votes), answered by jkuczm (7 votes)

================================== Greatest hits from previous weeks: ==================================

[How to manipulate 2D plots?] https://mathematica.stackexchange.com/questions/7142/how-to-manipulate-2d-plots

When it comes to visual analysis, large datasets or data with intricate internal details often makes plotting in 2D useless, as the outcome is either just a fraction of the full dataset, or no details ...

- asked by István Zachar (122 votes), answered by István Zachar (137 votes)

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[Mathematica erroneously says this integral does not converge] https://mathematica.stackexchange.com/questions/144965/mathematica-erroneously-says-this-integral-does-not-converge

Mathematica (as of v. 11.1.0) does not recognize that this special case of Frullani’s integral converges:

Integrate[(ArcTan[a*x] - ArcTan[b*x])/x, {x, 0, Infinity}]
(* Integrate::idiv: Integral of  ...

- asked by Pillsy (14 votes), answered by Michael E2 (20 votes)

================================== Can you answer these? ==================================

[Is there a good explanation of the output of FeatureExtract anywhere?] https://mathematica.stackexchange.com/questions/154044/is-there-a-good-explanation-of-the-output-of-featureextract-anywhere

I have been looking at the official documentation of FeatureExtract, and I’m having a bit of difficulty interpreting the output–or understanding the reasons for some of the choices that were made. ...

- asked by Shredderroy (1 vote)

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[How to work out sums symbolically?] https://mathematica.stackexchange.com/questions/153820/how-to-work-out-sums-symbolically

Intro

Consider these two equal expressions of the variance

∑            ∑
--ni=1x(i)2  (--ni=1-x(i))2
    n     −      n2

and

$$\frac{\sum _{i=1}^n \left(x(i)-\frac{\sum  ...

- asked by Remi.b (1 vote)

—————————-

[Expectation value of standard deviation] https://mathematica.stackexchange.com/questions/153848/expectation-value-of-standard-deviation

I was trying to calculate the expectation value of the standard deviation, if I only take two data points into account. My code is the following:

n[x_] = PDF[NormalDistribution[μ, σ], x];
σ2[x1_,  ...

- asked by Glostas (1 vote)

6 Tuesday, August 15, 2017

==================================
Top new questions this week:
==================================

[How to remove a paclet downloaded from Wolfram Research Server?] https://mathematica.stackexchange.com/questions/153752/how-to-remove-a-paclet-downloaded-from-wolfram-research-server

How can I remove a paclet that was automatically downloaded when I used a function for the first time (i.e. NetChain)?

I believe the download was faulty, preventing me from using any of the ...

- asked by mpourrah (8 votes), answered by Itai Seggev (10 votes)

—————————-

[Best way to expand vocabulary of Mathematica functions?] https://mathematica.stackexchange.com/questions/153469/best-way-to-expand-vocabulary-of-mathematica-functions

I’m enjoying slowly learning Mathematica but noticing one skill I’m lacking is a comprehensive vocabulary of Mathematica functions. I was wondering if members would mind sharing some strategies they ...

- asked by BBirdsell (8 votes), answered by Nasser (9 votes)

—————————-

[high pass filter without losing detail] https://mathematica.stackexchange.com/questions/153414/high-pass-filter-without-losing-detail

I have troubles doing a simple high pass filtering...

Downloading the test data https://pastebin.com/74J8t2YV as ”test.dat”, you can see that overimposed on the signal there are some low frequencies ...

- asked by alessandro (8 votes), answered by xzczd (7 votes)

—————————-

[Accesing keys based on position in an association] https://mathematica.stackexchange.com/questions/153689/accesing-keys-based-on-position-in-an-association

I would like to have the following simple function ”GetKey[]” on a very large association.

(* The actual Association is very large, this is just small example *)
assoc = &lt;|{1,1} -&gt; 2, {1,2}  ...

- asked by Iconoclast (7 votes), answered by Carl Woll (9 votes)

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[How to calculate CellularAutomaton rule numbers in higher dimensions?] https://mathematica.stackexchange.com/questions/153388/how-to-calculate-cellularautomaton-rule-numbers-in-higher-dimensions

Where can I find documentation of the rule number convention for CellularAutomaton for higher than 1 dimension?

I understand the convention for elementary 1D automata, but I don’t understand even ...

- asked by Mark S. (7 votes), answered by Vitaliy Kaurov (6 votes)

—————————-

[Clicking on any Line of Code causes Plotted Points to Vanish] https://mathematica.stackexchange.com/questions/153368/clicking-on-any-line-of-code-causes-plotted-points-to-vanish

Bug detected in 11.1, apparently related but not identical to bug in 10.4. Reported to Worfram, Inc as CASE:3926732

$Version
(* "11.1.1 for Microsoft Windows (64-bit) (April 18, 2017)" *)

p1 =  ...

- asked by bbgodfrey (7 votes), answered by John Joseph M. Carrasco (3 votes)

—————————-

[Puzzled about the behavior of NDSolve (ODE’s involving Integrals)] https://mathematica.stackexchange.com/questions/153624/puzzled-about-the-behavior-of-ndsolve-odes-involving-integrals

Any idea why NDSolve can easily handle the first of these examples, but not the 2nd? I have a system of ODE’s involving integrals without closed-form solutions, and keep getting the 2nd error message. ...

- asked by Andrea Wilson (6 votes), answered by Michael E2 (5 votes)

================================== Greatest hits from previous weeks: ==================================

[Labeling individual curves in Mathematica] https://mathematica.stackexchange.com/questions/4444/labeling-individual-curves-in-mathematica

I need to create a plot for export and inclusion in a report. Is there a better way to label curves than PlotLegends? From what I’ve read and my personal experience, PlotLegends is pretty bad.

Is ...

- asked by Tianxiang Xiong (52 votes), answered by Artes (40 votes)

—————————-

[Is there an open source implementation of Mathematica-the-language?] https://mathematica.stackexchange.com/questions/4454/is-there-an-open-source-implementation-of-mathematica-the-language

I’ve seen questions before such as ”What is the best open-source equivalent for Mathematica?”, but that specific question (and that line of inquiry in general) cares more about the computer algebra ...

- asked by sblom (88 votes), answered by Simon (68 votes)

================================== Can you answer these? ==================================

[Analysis of the periodic data by the maximum entropy method] https://mathematica.stackexchange.com/questions/153487/analysis-of-the-periodic-data-by-the-maximum-entropy-method

I am trying to get the frequency spectrum of a periodic data. Since the data set is short, the outcome of the frequency peaks are not sharp enough, which prevents me for further analysis. I know the ...

- asked by Phyman (1 vote)

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[Plotting InterpolationFunction over Quantities] https://mathematica.stackexchange.com/questions/153458/plotting-interpolationfunction-over-quantities

What’s the proper syntax to plot Interpolation functions defined over Quantities?

points = {{0, 0}, {1, 1}, {2, 3}, {3, 4}, {4, 3}, {5, 0}};


Change domain to Quantities:

points2 = points //  ...

- asked by alancalvitti (2 votes)

—————————-

[Fastest form of a function] https://mathematica.stackexchange.com/questions/153602/fastest-form-of-a-function

I’m trying to find the fastest form for a function. I have a few approaches with test results.The function I’m working with is the 3rd derivative of the incomplete beta function with respect to its ...

- asked by FalafelPita (1 vote)

7 Tuesday, August 8, 2017

==================================
Top new questions this week:
==================================

[Why can’t I inject expressions in Compile using (only) With] https://mathematica.stackexchange.com/questions/153064/why-cant-i-inject-expressions-in-compile-using-only-with

Generally speaking, With can be used to inject into arbitrarily held expressions, for example:

With[{args = 2},
  Hold @ Hold @ HoldComplete[args]
]
(* Out[1]= Hold[Hold[HoldComplete[2]]] *)
 ...

- asked by glS (14 votes), answered by Leonid Shifrin (15 votes)

—————————-

[Why Mathematica can not factorize polynomials over algebraic fields?] https://mathematica.stackexchange.com/questions/152949/why-mathematica-can-not-factorize-polynomials-over-algebraic-fields

I noticed that a factorization over algebraic fields is useless in Mathematica. Here is the example over the field containing I*Sqrt[3]:

Pol=4 (3 I Sqrt[3] (-12 + 6 x - 4 x^2 + x^3) y^3 z +
9 (12 -  ...

- asked by Aus Man (14 votes), answered by chyaong (11 votes)

—————————-

[RegionMeasure is wrong for simple 1D Path] https://mathematica.stackexchange.com/questions/153323/regionmeasure-is-wrong-for-simple-1d-path

Bug introduced in 11.1

Take the simple path defined by a line through a set of points

pts = {{0, 0}, {0, 1.5}, {0.05, 1.5}, {0.05, 0.5}, {0.1, 0.5}, {0.1,  1.5},
{0.15, 1.5}, {0.15, 0.5}, {0.2,  ...

- asked by Sascha (13 votes), answered by Michael E2 (8 votes)

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[Why am I seeing what looks like a violation of operator precedence?] https://mathematica.stackexchange.com/questions/153258/why-am-i-seeing-what-looks-like-a-violation-of-operator-precedence

Why is it that when I evaluate

2*2.848529281693615`+3*-0.5155083247776808`

I get

(* -2.93688 *)


which is wrong.

2*2.848529281693615` + (3*-0.5155083247776808`)
(* 4.15053 *)

Any help would be ...

- asked by An old man in the sea. (9 votes), answered by C. E. (9 votes)

—————————-

[Need a gentle introduction to stylesheet writing] https://mathematica.stackexchange.com/questions/153102/need-a-gentle-introduction-to-stylesheet-writing

I have searched Mathematica.SE for stylesheet and found a lot of useful information on specific issues but no general introduction. There were 746 hits, and it is very time consuming for anyone to ...

- asked by m_goldberg (9 votes), answered by m_goldberg (7 votes)

—————————-

[Unexpected behavior when directly assigning to DownValues] https://mathematica.stackexchange.com/questions/152999/unexpected-behavior-when-directly-assigning-to-downvalues

I’m encountering some unexpected behavior when assigning to DownValues. When I assign two definitions for test[1] as below, Mathematica stores both definitions:

DownValues[test] =  ...

- asked by tom (9 votes), answered by b3m2a1 (6 votes)

—————————-

[Except @ OptionsPattern[] affects OptionValue] https://mathematica.stackexchange.com/questions/152984/except-optionspattern-affects-optionvalue

The background

This example works as expected, small function with a special case rule:

foo // ClearAll
foo // Options = {"bar" -&gt; 1};

foo[x_, y : Except[_Rule], patt : OptionsPattern[]
 ...

- asked by Kuba (9 votes), answered by Mr.Wizard (7 votes)

================================== Greatest hits from previous weeks: ==================================

[Mathematica 10.0.x freezes in Initializing kernels] https://mathematica.stackexchange.com/questions/92931/mathematica-10-0-x-freezes-in-initializing-kernels

Bug caused by paclet update and fixed by paclet update.

I updated to Windows 10 and have been running Mathematica fine on it for over a month. For some reason, it has just stopped working. I don’t ...

- asked by mitcheljh (73 votes), answered by ilian (95 votes)

—————————-

[Exporting graphics to PDF - huge file] https://mathematica.stackexchange.com/questions/1542/exporting-graphics-to-pdf-huge-file

I want to draw some basic surfaces, export them to PDF and include them in a LaTeX file. I create a simple 3D graphics object, for instance with

 ParametricPlot3D[{r Cos[θ], r Sin[θ], r^2}, {r, 0,  ...

- asked by Matthew Leingang (94 votes), answered by Heike (80 votes)

================================== Can you answer these? ==================================

[Operator on a multivariable function in a sum] https://mathematica.stackexchange.com/questions/153092/operator-on-a-multivariable-function-in-a-sum

I need to define an operator that does as follow for any function hm  .

$\qquad O[h_m](k,M,b,l_{max})=\sum_{l\neq (0,m)}^{l_{max}}il \left (h_l(k,M,b,l_{max}) b_{m-l}(k)- c_l\partial_k  ...

- asked by Michael_J (1 vote)

—————————-

[Direct input in Chinese, Korean or Japanese] https://mathematica.stackexchange.com/questions/153042/direct-input-in-chinese-korean-or-japanese

Sometimes I need to create a document in Japanese: I know Mathematica supports typing in Japanese. However it doesn’t seem to support direct (inline) input in Japanese.

Whenever I need to convert a ...

- asked by Tadashi Kikuno (5 votes)

—————————-

[Parametric Plot of Faces] https://mathematica.stackexchange.com/questions/152909/parametric-plot-of-faces

In How do I draw a pair of buttocks? there is a discussion how to draw a human backside. It shows an example of Manipulate to ParametricPlot3D this part of a body.

In this discussion they were ...

- asked by Adalbert Hanßen (1 vote)

8 Tuesday, August 1, 2017

==================================
Top new questions this week:
==================================

[String operation 1000X slower for special characters] https://mathematica.stackexchange.com/questions/152293/string-operation-1000x-slower-for-special-characters

It seems that the string operation is very slow if we have special characters in the string. Consider this example,

str =
  StringJoin@
   RandomChoice[Join[Alphabet[], ToString /@ Range[0, 9]],  ...

- asked by xslittlegrass (12 votes), answered by Alexey Popkov (12 votes)

—————————-

[Making a website with Mathematica] https://mathematica.stackexchange.com/questions/152663/making-a-website-with-mathematica

I know many people here have various websites associated with them and I’m guessing do at least some of the development of that stuff in Mathematica.

I recently fell down that rabbit hole myself, ...

- asked by b3m2a1 (11 votes), answered by C. E. (9 votes)

—————————-

[Convert association with list key to nested assocations] https://mathematica.stackexchange.com/questions/152676/convert-association-with-list-key-to-nested-assocations

I have an association that maps x, y pairs to values, for example:

 &lt;|{0, 0} -&gt; "a", {-1, -4} -&gt; "b", {-1, 1} -&gt; "c", {-1, 0} -&gt; "d", {1, 0} -&gt; "e"|&gt;

I want to convert this ...

- asked by 2012rcampion (9 votes), answered by MarcoB (8 votes)

—————————-

[Matching (y/x)^u terms wherever the appear in an expression] https://mathematica.stackexchange.com/questions/152559/matching-y-xu-terms-wherever-the-appear-in-an-expression

Mathematica keeps rewriting expressions, so it is hard to figure what pattern to use.

I am trying to replace all occurrences of y
x  by t  , but Mathematica re-writes ...

- asked by Nasser (9 votes), answered by aardvark2012 (4 votes)

—————————-

[Bulletproofing packages against SetOptions of built-ins] https://mathematica.stackexchange.com/questions/152472/bulletproofing-packages-against-setoptions-of-built-ins

Packages are (obviously) written in terms of built-in Mathematica functions. But many (if not, most) of these functions have options, like Expand, Solve, Compile

While a package is active, the user ...

- asked by QuantumDot (9 votes), answered by Leonid Shifrin (12 votes)

—————————-

[How can I offset a curve from the given data points?] https://mathematica.stackexchange.com/questions/152298/how-can-i-offset-a-curve-from-the-given-data-points

I am new to Mathematica programming.

I have a question related to my work with this software.

I have the data points below:

{{128.011, 86.7748}, {128.011, 86.7748}, {128.167, 86.7663}, {128.19,  ...

- asked by Mukidi Lee (8 votes), answered by J. M. (12 votes)

—————————-

[Export[..., ”tsv”] drops minus signs from Dataset [horrific bug?]] https://mathematica.stackexchange.com/questions/152355/export-tsv-drops-minus-signs-from-dataset-horrific-bug

Toy example:

First, create a Dataset:

data = Dataset[{&lt;|"x" -&gt;  1, "y" -&gt; -2|&gt;,
                &lt;|"x" -&gt; -3, "y" -&gt;  4|&gt;}]

Next, export it as a TSV file:

...

- asked by kjo (8 votes), answered by Rolf Mertig (6 votes)

================================== Greatest hits from previous weeks: ==================================

[Entering numbers in Scientific Notation?] https://mathematica.stackexchange.com/questions/36792/entering-numbers-in-scientific-notation

I need to play with a lot of powers such as 10^-3. 1E-3 does not work for it. Is there any short form for it?

- asked by hhh (32 votes), answered by Rahul (43 votes)

—————————-

[Creating legends for plots with multiple lines?] https://mathematica.stackexchange.com/questions/4025/creating-legends-for-plots-with-multiple-lines

So I have a graph with multiple lists, for e.g.

data = {{1,2}, {3,4}, {3,5}, {2,3} . . .}


If I then do ListLinePlot[Table[{#1,Log[b,#2]}&amp;@@@data, {b,1,10,2}]] I have
no way to generate a legend  ...

- asked by Eiyrioü von Kauyf (60 votes), answered by Jens (90 votes)

================================== Can you answer these? ==================================

[Obstacle problem for the heat equation] https://mathematica.stackexchange.com/questions/152491/obstacle-problem-for-the-heat-equation

Consider the problem

$$\begin{cases}
\max\{\Delta u -\partial_t u, \varphi - u \} = 0 &amp; \text{ in } (0,T)\times \mathbb{R}^n \\
u(0,\cdot) = \varphi(0,\cdot) &amp; \text{ in } \mathbb{R}^n.
 ...

- asked by Hiro (3 votes)

—————————-

[DateListPlot of multiple time series with data values and legend appearing as the cursor moves over ploted lines] https://mathematica.stackexchange.com/questions/152405/datelistplot-of-multiple-time-series-with-data-values-and-legend-appearing-as-th

This is very similar to my previous question. I want to use ”DateListPlot” to visualize multiple time series (n) and see data values and legend as I move the cursor over plotted lines. To begin with, ...

- asked by ramesh (2 votes)

—————————-

[Using FindMinimum for a table of functions] https://mathematica.stackexchange.com/questions/152595/using-findminimum-for-a-table-of-functions

I am relatively new to Mathematica and am having trouble with my code running quite slowly. What I am attempting to do is find the minimum value of a function (a chi^2) of one fit variable, but this ...

- asked by nsbd88 (1 vote)

9 Tuesday, July 25, 2017

==================================
Top new questions this week:
==================================

[Reduce Code Length] https://mathematica.stackexchange.com/questions/152003/reduce-code-length

I have the following that works good, and computes in one shot,but the code is so long. Can someone please help me to reduce the size of this?

...

- asked by Bill W. (9 votes), answered by Ali Hashmi (7 votes)

—————————-

[Best way to handle nested Maps?] https://mathematica.stackexchange.com/questions/151742/best-way-to-handle-nested-maps

I often find myself working with lists of lists of data, gathering data, performing computations, and producing a variety of different sorts of output. Intuitively, it seems like this should be done ...

- asked by Michael Stern (9 votes), answered by eldo (6 votes)

—————————-

[Color gradient varying in a path] https://mathematica.stackexchange.com/questions/151980/color-gradient-varying-in-a-path

The code below is to create something like a logo. I want to apply a color gradient over the polygons of the pattern, but they vary along the path. The image that I want to approach is this:

ang = ...

- asked by LCarvalho (8 votes), answered by KennyColnago (9 votes)

—————————-

[Offset Partition with only one remainder element] https://mathematica.stackexchange.com/questions/152152/offset-partition-with-only-one-remainder-element

I would like to use a combination of options of Partition in a way that I can’t seem to find in the documentation.

Given example input {a,b,c,d,e,f,g}, I would like output  ...

- asked by George Moore (7 votes), answered by kglr (4 votes)

—————————-

[Slot # corresponding to subset of a list in select] https://mathematica.stackexchange.com/questions/152082/slot-corresponding-to-subset-of-a-list-in-select

Is it possible to use # in the select function preserving the structure of the list?

Here an example of what I mean. Lets say I want to select all the pairs
where the first element is 1:

data1 =  ...

- asked by Fraccalo (7 votes), answered by kglr (7 votes)

—————————-

[Any faster approach than Outer for my computation] https://mathematica.stackexchange.com/questions/151892/any-faster-approach-than-outer-for-my-computation

Outer is slowing down considerably when the first argument is Abs[#1 - #2]/Max[#1, #2]&amp;

Outer[List, Range[5000], Range[5000]]; // AbsoluteTiming
(* {0.120091, Null} *)

Outer[Abs[#1 -  ...

- asked by Ali Hashmi (6 votes), answered by nikie (9 votes)

—————————-

[How to generate password] https://mathematica.stackexchange.com/questions/151864/how-to-generate-password

I would like to generate a random password of a defined length which can easily be typed in with a standard keyboard.

As a start I tried the following:

SeedRandom["pass"];
 ...

- asked by mrz (6 votes), answered by yohbs (11 votes)

================================== Greatest hits from previous weeks: ==================================

[Why should I avoid the For loop in Mathematica?] https://mathematica.stackexchange.com/questions/134609/why-should-i-avoid-the-for-loop-in-mathematica

Some people advise against the use of For loops in Mathematica. Why? Should I heed this advice? What is wrong with For? What should I use instead?

- asked by Szabolcs (52 votes), answered by Szabolcs (62 votes)

—————————-

[Why round to even integers?] https://mathematica.stackexchange.com/questions/2116/why-round-to-even-integers

According to the Mathematica help:

Round rounds numbers of the form x.5 toward the nearest even integer.

For example:

Round[{0.5, 1.5, 2.5, 3.5, 4.5}]


gives

{0, 2, 2, 4, 4}

- asked by wxffles (64 votes), answered by Per Alexandersson (42 votes)

================================== Can you answer these? ==================================

[How can I exclude factors containing a certain symbol form matching my pattern] https://mathematica.stackexchange.com/questions/151971/how-can-i-exclude-factors-containing-a-certain-symbol-form-matching-my-pattern

Ok, I give up. I can’t figure how to tell Mathematica to do replacement using a pattern except for some special case. Easier to explain with small example.

I want to change  pattern Exp[any_. c] to c  ...

- asked by Nasser (3 votes)

—————————-

[Graphics3D with explicit ViewAngle inside Manipulate disappears for a moment when starting rotation] https://mathematica.stackexchange.com/questions/151978/graphics3d-with-explicit-viewangle-inside-manipulate-disappears-for-a-moment-whe

Given the following:

Manipulate[
    ContourPlot3D[
        x^4 + y^4 + z^4 - (x^2 + y^2 + z^2)^2 + 3 (x^2 + y^2 + z^2) == 3 c,
        {x, -3, 3},
        {y, -3, 3},
        {z, -3, 3},
         ...

- asked by Mark (1 vote)

—————————-

[MTensor from existing memory?] https://mathematica.stackexchange.com/questions/151780/mtensor-from-existing-memory

I am wondering whether it’s possible to return a tensor from my C++ code using LibraryLink without copying the memory (because it’s large). So, instead of

libData-&gt;MTensor_new(..., &amp;T0);
 ...

- asked by mrupp (2 votes)

10 Tuesday, July 18, 2017

==================================
Top new questions this week:
==================================

[Is there concise code for the list operation I want to perform?] https://mathematica.stackexchange.com/questions/151550/is-there-concise-code-for-the-list-operation-i-want-to-perform

Is there any concise syntax for the following partitioning of a list. Given 1, 2, 3, 4, I want to get the output as shown below. I have tried various function such as Partition and others, but I ...

- asked by vikas (10 votes), answered by kglr (16 votes)

—————————-

[Animate Koch curve generation and include a transition effect] https://mathematica.stackexchange.com/questions/151621/animate-koch-curve-generation-and-include-a-transition-effect

Recently, I saw two kinds of animation of Koch curve iteration generation.

I don’t know how to make this effect, now I can only do this

Clear[koch];
koch[{A_, B_}] :=
  Partition[
    {A, (2 A  ...

- asked by mathe (10 votes), answered by Kuba (14 votes)

—————————-

[How to find the sum for each individual row in a binary matrix until the first zero is reached from left to right.] https://mathematica.stackexchange.com/questions/151396/how-to-find-the-sum-for-each-individual-row-in-a-binary-matrix-until-the-first-z

I have a 150 by 300 binary matrix. I would like to sum the 1’s for each individual row (from left to right) until the first zero is encountered. For example, if a given row is 1 1 1 1 1 1 0 0 0 1 0 0  ... 

- asked by Tiffany Visgaitis (7 votes), answered by eldo (8 votes)

—————————-

[Replace element in array by checking condition in another list] https://mathematica.stackexchange.com/questions/151293/replace-element-in-array-by-checking-condition-in-another-list

Im trying to escape doing double loops given the large number of items in the arrays.

I have two list with a format like this:

list1={{1,2,0},{1,3,0},{4,6,0},{2,3,0}} (*Third element of each item is  ...

- asked by Giovanni Baez (7 votes), answered by Carl Woll (8 votes)

—————————-

[Geometry computations add-on for Mathematica?] https://mathematica.stackexchange.com/questions/151304/geometry-computations-add-on-for-mathematica

I came across the problem of calculating the circumcenters of triangles symbolically within another algorithm (as well as possibly doing other similar geometry computations). I was hoping Mathematica ...

- asked by Grayscale (7 votes), answered by C. E. (10 votes)

—————————-

[Trace of the points of intersection of two moving curves] https://mathematica.stackexchange.com/questions/151325/trace-of-the-points-of-intersection-of-two-moving-curves

I would like to trace the points of intersection between the polar curves

r == Cos[n θ + k t]


and

r == t Csc[θ]

as t goes from -1 to 1. (n and k are constants, and y, r, and θ relate in the  ...

- asked by 404UserNotFound (6 votes), answered by Carl Woll (11 votes)

—————————-

[How to delete the parameter of a Neural Network?] https://mathematica.stackexchange.com/questions/151591/how-to-delete-the-parameter-of-a-neural-network

Mathematica Neural Networks based on MXNet. And there is lots of model in MXNet(MXNet Model Zoo).

For example,I follow a tutorial An introduction to the MXNet API — part 4, It uses Inception v3(net ...

- asked by partida (5 votes), answered by xslittlegrass (3 votes)

================================== Greatest hits from previous weeks: ==================================

[Why should I avoid the For loop in Mathematica?] https://mathematica.stackexchange.com/questions/134609/why-should-i-avoid-the-for-loop-in-mathematica

Some people advise against the use of For loops in Mathematica. Why? Should I heed this advice? What is wrong with For? What should I use instead?

- asked by Szabolcs (52 votes), answered by Szabolcs (62 votes)

—————————-

[Image processing: Floor plan - detecting rooms’ borders (area) and room names’ texts] https://mathematica.stackexchange.com/questions/19546/image-processing-floor-plan-detecting-rooms-borders-area-and-room-names-t

Here is a simple building floor plan. I would like to derive the rooms as (rectangular) components and the names of the rooms. This is very common representation of building floor plans.

The ...

- asked by s.s.o (52 votes), answered by nikie (52 votes)

================================== Can you answer these? ==================================

[Unexpected Behavior of Parametric Sensitivity in ParametricNDSolveValue] https://mathematica.stackexchange.com/questions/151294/unexpected-behavior-of-parametric-sensitivity-in-parametricndsolvevalue

While exploring alternative methods of solving 33538, I encountered difficulties with the parametric sensitivity capability of ParametricNDSolveValue. (Useful background on parametric sensitivity is ...

- asked by bbgodfrey (2 votes)

—————————-

[FindShortestTour suddenly runs far slower for large numbers of points] https://mathematica.stackexchange.com/questions/151513/findshortesttour-suddenly-runs-far-slower-for-large-numbers-of-points

I was doing a benchmark of FindShortestTour and I noticed something really weird. Around 10000 points, FindShortestTour suddenly takes 6 times as long without explanation:

times = Table[
    pts =  ...

- asked by Jorge Perez (2 votes)

—————————-

[Manual CellGroups: problem with closing nested CellGroupData] https://mathematica.stackexchange.com/questions/151336/manual-cellgroups-problem-with-closing-nested-cellgroupdata

Background

CellGroupData second argument allows to specify which cells are visible. I faced problems though.

This example works well, the second group is not visible:

Notebook[{
   Cell @  ...

- asked by Kuba (1 vote)

11 Tuesday, July 11, 2017

==================================
Top new questions this week:
==================================

[Replace elements that do not match a pattern] https://mathematica.stackexchange.com/questions/149736/replace-elements-that-do-not-match-a-pattern

I have the following matrix

mat={{0,a,b},{c,0,d},{0,0,e}}

I would like to replace the zero elements of it with 1 and the remaining with zero. The first step would be

mat/.{0-&gt;1}

However I ...

- asked by Galuoises (12 votes), answered by eldo (7 votes)

—————————-

[Image segmentation by pixel value] https://mathematica.stackexchange.com/questions/149966/image-segmentation-by-pixel-value

I’m looking for a way to segment a grayscale image (or a 2D array) by its pixel values. We look at two neighboring pixels, if their values are close within a certain threshold, then we say they are ...

- asked by xslittlegrass (11 votes), answered by nikie (11 votes)

—————————-

[Can trees be made into graphs?] https://mathematica.stackexchange.com/questions/151155/can-trees-be-made-into-graphs

When one has the output of a function like TreeForm, for instance:

Can this be turned into a Graph object? I would like to be able to apply functions like VertexList, VertexDegree, AdjacencyList, ...

- asked by M. Brandt (8 votes), answered by C. E. (5 votes)

—————————-

[Layout tips to keep UI responsive] https://mathematica.stackexchange.com/questions/149835/layout-tips-to-keep-ui-responsive

Bug introduced in V10.4 or earlier and persisting through V11.1.1

  CASE:3914402


Here is an example of a problem I have. Gutted version of something much bigger:

handler2 =  Framed[#,     ...

- asked by Kuba (8 votes), answered by Kuba (1 vote)

—————————-

[How to use LATEXin Mathematica text] https://mathematica.stackexchange.com/questions/151102/how-to-use-latex-in-mathematica-text

I would like to formulate a question in a notebook for my students using LATEX(or MathML) to typeset functions and matrices. I specifically want a language other than Mathematica as students ...

- asked by user49947 (7 votes), answered by Nasser (6 votes)

—————————-

[getting zero for special positions in a matrix] https://mathematica.stackexchange.com/questions/149767/getting-zero-for-special-positions-in-a-matrix

There are a list

list={{1, 2, 3, 2, 3}, {3, 1, 1, 2, 3}, {3, 2, 1, 3, 2}, {1, 2, 1, 1, 1}};


I wish to have all elements be zero except the first
and the fourth in each row: desired:

list={{1, 0,  ...

- asked by Irreversible (7 votes), answered by tomd (7 votes)

—————————-

[To Work with Barchart or DiscretePlot?] https://mathematica.stackexchange.com/questions/149960/to-work-with-barchart-or-discreteplot

I would like to create a graph similar to this below using some slightly dotted bar style like the one shown in the figure ...

And I’m trying to open a space between bars 6 and 8, but I’m failing.

...

- asked by LCarvalho (7 votes), answered by kglr (6 votes)

================================== Greatest hits from previous weeks: ==================================

[How to manipulate 2D plots?] https://mathematica.stackexchange.com/questions/7142/how-to-manipulate-2d-plots

When it comes to visual analysis, large datasets or data with intricate internal details often makes plotting in 2D useless, as the outcome is either just a fraction of the full dataset, or no details ...

- asked by István Zachar (117 votes), answered by István Zachar (134 votes)

—————————-

[Learn Mathematica (Wolfram) Language in one day] https://mathematica.stackexchange.com/questions/138366/learn-mathematica-wolfram-language-in-one-day

Currently I am trying to learn Python. Searching for relevant material I came across

X in Y minutes

and books with titles such as Learn Python in one day, in 24 hours, etc.

Similar material exists ...

- asked by dimitris (25 votes), answered by masterxilo (9 votes)

================================== Can you answer these? ==================================

[Sorting a list of rules] https://mathematica.stackexchange.com/questions/149862/sorting-a-list-of-rules

When we give several definitions for a function f, the DownValues of f are automatically sorted with respect to the domain defined by the pattern:

f[x_]:=2;
f[x_?Positive] := 3;
f[1]=4;
 ...

- asked by Fred Simons (3 votes)

—————————-

[Plotting orbits of trajectories of bodies sharing the earth’s orbit in coordinates centered at the barycenter of the solar system] https://mathematica.stackexchange.com/questions/151069/plotting-orbits-of-trajectories-of-bodies-sharing-the-earths-orbit-in-coordinat

I am attempting to try and plot the trajectories of a trio of satellites that are orbiting with the earth-moon system around the solar system’s barycenter. Originally, I had the satellites in orbit ...

- asked by SSoltero (1 vote)

—————————-

[Mathematica not releasing RAM] https://mathematica.stackexchange.com/questions/151127/mathematica-not-releasing-ram

The following code is supposed to sequentially read data from a large CSV file and put it row by row into an SQL server. Although I thought RAM consumption should be constant the system keeps asking ...

- asked by user13892 (2 votes)

12 Tuesday, July 4, 2017

==================================
Top new questions this week:
==================================

================================== Top new questions this week: ==================================

[Is there a simple and fast way to delete dependent lines of a matrix] https://mathematica.stackexchange.com/questions/149281/is-there-a-simple-and-fast-way-to-delete-dependent-lines-of-a-matrix

I am building a matrix, but some of the lines are dependant. I would like to only keep independant lines (so erase all lines that depend from another).

I could compute the nullspace of the transpose ...

- asked by StarBucK (10 votes), answered by george2079 (10 votes)

—————————-

[Vertex coloring for bi-connected graphs] https://mathematica.stackexchange.com/questions/149247/vertex-coloring-for-bi-connected-graphs

In graph theory, a bi-connected component is a maximal bi-connected subgraph of a graph g  –i.e., a connected subgraph that would remain connected if any one of its vertexes were to be removed. An ...

- asked by David G. Stork (10 votes), answered by kglr (9 votes)

—————————-

[Compile and uncompilable function bug?] https://mathematica.stackexchange.com/questions/149343/compile-and-uncompilable-function-bug

I think I found a bug, but I still have MMA version 11.0.1 installed. Can somebody please check if this persists in the latest version?

When I compile this function:

cf = Compile[{{n, _Integer}},
   ...

- asked by JEM_Mosig (10 votes), answered by Michael E2 (12 votes)

—————————-

[How to make the result of InputForm balance the bracket] https://mathematica.stackexchange.com/questions/149558/how-to-make-the-result-of-inputform-balance-the-bracket

I always use InputForm to check the result object,such as Dataset or Graphics or other objects.But if you are in the result of InputForm,you cannot use the Front-End function of balance the bracket. ...

- asked by yode (9 votes), answered by Carl Woll (6 votes)

—————————-

[KeyValuePattern in matching and replacement in nested associations] https://mathematica.stackexchange.com/questions/149402/keyvaluepattern-in-matching-and-replacement-in-nested-associations

This case revealed I am missing something in pattern matching and evaluation in case of match, or I can’t grasp it due to the busy week I have. Either way, I find this problem interesting for wider ...

- asked by Kuba (9 votes), answered by Mr.Wizard (5 votes)

—————————-

[Align two images with respect to sperm head] https://mathematica.stackexchange.com/questions/149280/align-two-images-with-respect-to-sperm-head

My biologist friend has to align sperm images according to their heads. He usually does that manually by rotating each image. The problem is that there are so many images and it takes a lot of time. ...

- asked by Anjan Kumar (9 votes), answered by nikie (7 votes)

—————————-

[A more convenient Fourier series] https://mathematica.stackexchange.com/questions/149468/a-more-convenient-fourier-series

Personally, I feel the design of FourierSeries/FourierSinSeries/FourierCosSeries/FourierTrigSeries not convenient enough because:

They can’t give general formula of series as output, one must set a ...

- asked by xzczd (7 votes), answered by xzczd (7 votes)

================================== Greatest hits from previous weeks: ==================================

[Why should I avoid the For loop in Mathematica?] https://mathematica.stackexchange.com/questions/134609/why-should-i-avoid-the-for-loop-in-mathematica

Some people advise against the use of For loops in Mathematica. Why? Should I heed this advice? What is wrong with For? What should I use instead?

- asked by Szabolcs (51 votes), answered by Szabolcs (61 votes)

—————————-

[My Girlfriend is going to prison...Save her with Math] https://mathematica.stackexchange.com/questions/135937/my-girlfriend-is-going-to-prison-save-her-with-math

Salacious title, but true story.

 dmethyl1 = {
      {0, 0},
      {.25, 1},
      {.5, 7},
      {1, 26},
      {1.5, 40},
      {2, 45},
      {2.5, 45},
      {3, 44},
      {3.5, 44},
      {4,  ...

- asked by Prisoners Dilema (39 votes), answered by bobthechemist (24 votes)

================================== Can you answer these? ==================================

[Serious regression in Integrate in 11.1.1? Division by zero generated] https://mathematica.stackexchange.com/questions/149495/serious-regression-in-integrate-in-11-1-1-division-by-zero-generated

What is going on here? In version 11.1.1 on windows 7

Using Version 11.0.1 also on windows 7

Source code

ClearAll[x, n, c, a ,b]
Integrate[(a + b*(c*x^n)^(2/n))^3, x]

Why does ...

- asked by Nasser (7 votes)

—————————-

[Hiding inputs with specific function] https://mathematica.stackexchange.com/questions/149298/hiding-inputs-with-specific-function

I believe this question could be a duplication, but I did some searches with the term ”hide the input cell”, but none answered me. Only inputs with this function.

I have several input cells using the ...

- asked by LCarvalho (3 votes)

—————————-

[Gravitational Lensing Simulation, Coordinate and Rendering Issues] https://mathematica.stackexchange.com/questions/149447/gravitational-lensing-simulation-coordinate-and-rendering-issues

I am trying to replicate this gravitational simulation online application called LensToy using Mathematica instead. I have two issues.

First, unlike LensToy, my rendering is extremely slow and drives ...

- asked by mpourrah (2 votes)

13 Tuesday, June 27, 2017

==================================
Top new questions this week:
==================================

[Display 10^n as power] https://mathematica.stackexchange.com/questions/148794/display-10n-as-power

How can I tell MMA to display input of the form 10^n as 10n  and not e.g. as 1000 for n = 3  or the rational -1--
1000   for n = − 3  .

This would help to keep tables compact when some ...

- asked by Casimir (13 votes), answered by eldo (10 votes)

—————————-

[How to remove unknown zero-width character from string?] https://mathematica.stackexchange.com/questions/148899/how-to-remove-unknown-zero-width-character-from-string

I have text that contains a zero-width character that I am not able to remove. A minimum example is in str below where the character is at the start of the text.

str = "​4-6";
res = ToExpression /@  ...

- asked by Edmund (12 votes), answered by Carl Woll (10 votes)

—————————-

[Series sum approximation] https://mathematica.stackexchange.com/questions/149090/series-sum-approximation

Since there is no closed formula, as far as I know, to find the sum of

∑∞   (− 1)n
    ∘-------
n=2   log (n )

I used //N to find an approximation and Mathematica gave me ...

- asked by Raffaele (11 votes), answered by TeM (18 votes)

—————————-

[How to extract first 9 rows from every block of 22 rows?] https://mathematica.stackexchange.com/questions/149026/how-to-extract-first-9-rows-from-every-block-of-22-rows

I’m working with a list of lists (a large table).

How would I extract the first 9 rows from every 22 rows of this list?

Essentially, I’d like to drop rows 10 to 22, and then 32 to 44, and so on, ...

- asked by musicmaker (11 votes), answered by C. E. (11 votes)

—————————-

[Confusion about HoldFirst attribute of Set] https://mathematica.stackexchange.com/questions/148956/confusion-about-holdfirst-attribute-of-set

Set has the attribute HoldFirst. Expectedly the following does not work, i.e. it does not assign the OwnValue of 3 to x:

In[1]:= {x, y}[[1]] = 3

During evaluation of In[1]:= Set::setps: {x,y} in the  ...

- asked by kalix (8 votes), answered by Kuba (10 votes)

—————————-

[What algorithm is Mathematica using to find the smallest eigenvalue so quickly?] https://mathematica.stackexchange.com/questions/148759/what-algorithm-is-mathematica-using-to-find-the-smallest-eigenvalue-so-quickly

My question is what kind of black magic is Mathematica doing to obtain the correct answer so quickly compared to other programming languages?

Details:

I’ve written a Mathematica notebook to find the ...

- asked by Daniel Walsh (8 votes)

—————————-

[Simplify expression with Sqrt] https://mathematica.stackexchange.com/questions/149186/simplify-expression-with-sqrt

Hi folks I have a simple Simplify[] question

the following expression simplifies nice:

Sqrt[4 (a + b) - 4 c] // Simplify
2 Sqrt[a + b - c]


the next one refuses

Sqrt[4 (a + b) - 4 (c + d)] //  ...

- asked by Robert Nowak (6 votes), answered by Shadowray (5 votes)

================================== Greatest hits from previous weeks: ==================================

[Calculate the 2D Fourier transform of an Image] https://mathematica.stackexchange.com/questions/29203/calculate-the-2d-fourier-transform-of-an-image

I am new to Mathematica, and using version 8.0.

I would like to calculate the 2D Fourier Transform of an Image with Mathematica and plot the magnitude and phase spectrum, as well as reconstruct the ...

- asked by user8727 (5 votes), answered by Nasser (27 votes)

—————————-

[Entering numbers in Scientific Notation?] https://mathematica.stackexchange.com/questions/36792/entering-numbers-in-scientific-notation

I need to play with a lot of powers such as 10^-3. 1E-3 does
not work for it. Is there any short form for it?

- asked by hhh (32 votes), answered by Rahul (43 votes)

================================== Can you answer these? ==================================

[Cross-section of graph] https://mathematica.stackexchange.com/questions/148902/cross-section-of-graph

I am trying to use the following code to plot the cross-section
of the graph z=x^2+y^2 and x=t. I use Manipulate to vary t.

h = z - x^2 - y^2;
g = x;
Manipulate[
 Show[
  ContourPlot3D[{h == 0, g ==  ...

- asked by henryforever14 (1 vote)

—————————-

[How to embed Mathematica or Wolfram Alpha results in a website] https://mathematica.stackexchange.com/questions/149063/how-to-embed-mathematica-or-wolfram-alpha-results-in-a-website

Is it possible to dynamically embed responses into a blog post?

So the user would see:

There are 390900 plant species in the world.

With pseudo code:

There are #{worlfram(number of plant species)}  ...

- asked by Mr. Demetrius Michael (1 vote)

—————————-

[Package MathWorld] https://mathematica.stackexchange.com/questions/148837/package-mathworld

I’m looking for MathWorld packages, but I can not find anywhere. I found an question that came very close but did not help me.

I got lost on the site and did not find anything.

I need to use the ...

- asked by LCarvalho (4 votes)

14 Tuesday, June 20, 2017

==================================
Top new questions this week:
==================================

[Good references for parallel programming in Mathematica] https://mathematica.stackexchange.com/questions/148489/good-references-for-parallel-programming-in-mathematica

There are plenty of good references for all sorts of Mathematica programming:

This forum is a great example for specific questions/”getting things done”. Books like those by R.Maeder (esp. the now ...

- asked by Gaius (17 votes)

—————————-

[Dot not well-defined: are there better examples?] https://mathematica.stackexchange.com/questions/148465/dot-not-well-defined-are-there-better-examples

Dot is not ”well-defined” in Mathematica - we cannot simultaneously have it being associative and working with 1D and 2D arrays. For example, the order we substitute for variables should not change ...

- asked by mikado (10 votes), answered by Shadowray (9 votes)

—————————-

[Internal‘Bag memory usage] https://mathematica.stackexchange.com/questions/148594/internalbag-memory-usage

1. How does Internal‘Bag handle memory inside a compiled function? (examples below)

2. Is there a way to explicitly free up memory used by Internal‘Bag without exiting the function?

Preface: The ...

- asked by aardvark2012 (9 votes)

—————————-

[Preventing an unwanted vertical line from appearing my plot] https://mathematica.stackexchange.com/questions/148502/preventing-an-unwanted-vertical-line-from-appearing-my-plot

How can I eliminate (remove) the unwanted vertical line x = 1 when I make the plot shown below.

p3 =
  Plot[
    {0.5/(-0.1 x + 0.1),
     0.04/(-0.004 x + 0.004),
     1.359/(-0.08 x + 0.08),
    ...

- asked by Irreversible (9 votes), answered by m_goldberg (1 vote)

—————————-

[Integer to Alpha Representation] https://mathematica.stackexchange.com/questions/148446/integer-to-alpha-representation

I wanted a nice way to convert natural numbers to alphabetic representations like:

1-&gt;"A",
2-&gt;"B",
...
26-&gt;"Z",
27-&gt;"AA,
...
26*2-&gt;"AZ",
26*2+1-&gt;"BA",
...

And I knew this was ...

- asked by b3m2a1 (8 votes), answered by Carl Woll (6 votes)

—————————-

[How to display numbers as multiples of a square root] https://mathematica.stackexchange.com/questions/148551/how-to-display-numbers-as-multiples-of-a-square-root

The extension field    √ -- √ --
ℚ (  2+   3)  can be represented by a 4  - dimensional vector space over ℚ  with basis    √ --√ --√ --
{1,  2,  3,  6} .

I made a matrix ...

- asked by nilo de roock (8 votes), answered by Carl Woll (7 votes)

—————————-

[Visually permute rows of a matrix via mouse dragging] https://mathematica.stackexchange.com/questions/148448/visually-permute-rows-of-a-matrix-via-mouse-dragging

I’m looking for a way to permute the rows of a matrix visually via mouse dragging, for example by clicking and dragging on a row in the MatrixPlot corresponding to the matrix.

What would be the best ...

- asked by glS (8 votes), answered by glS (10 votes)

================================== Greatest hits from previous weeks: ==================================

[How to tell Mathematica that certain variables are real/imaginary, integer-valued, etc] https://mathematica.stackexchange.com/questions/66273/how-to-tell-mathematica-that-certain-variables-are-real-imaginary-integer-value

I’m trying to expedite some quantum mechanical calculations (expectation values etc.) by running them through Mathematica. When I say, for example,

u[x_] := Sqrt[2/L] * Sin[Pi * n * x / L]

and then ...

- asked by Matthew Brunetti (17 votes), answered by SquareOne (11 votes)

—————————-

[Entering numbers in Scientific Notation?] https://mathematica.stackexchange.com/questions/36792/entering-numbers-in-scientific-notation

I need to play with a lot of powers such as 10^-3. 1E-3
does not work for it. Is there any short form for it?

- asked by hhh (32 votes), answered by Rahul (43 votes)

================================== Can you answer these? ==================================

[Which method should I use for a numerical triple Integration?] https://mathematica.stackexchange.com/questions/148629/which-method-should-i-use-for-a-numerical-triple-integration

Which method should I use for this numerical integration? Does it converge?

My constants are:

P = 10.5;
m = 48.2;
c = 1;
α = 0.01;
V0 = 10;
EE = 2.3;
II = 1.;
k = 68.9*10^3;


My Integration is

    ...

- asked by Edmond Muho (2 votes)

—————————-

[possible memory problem with WatershedComponents] https://mathematica.stackexchange.com/questions/148318/possible-memory-problem-with-watershedcomponents

This could be regarded as a follow-up question to a previous post of mine (link).

When I use the WatershedComponents function on a large image (about 6000 x 10000 pixels) Mathematica comes up with an ...

- asked by Kardashev3 (4 votes)

—————————-

[Swedish characters in Databin] https://mathematica.stackexchange.com/questions/148550/swedish-characters-in-databin

I want to store strings with Swedish characters like å, ä and ö in a Databin, but get the following result:

bin = CreateDatabin[];
DatabinUpload[bin, {"a", "ä"}];
Values[bin]
{a,"a""}

Does anyone ...

- asked by Sverker (5 votes)

15 Tuesday, June 13, 2017

==================================
Top new questions this week:
==================================

[Same region, different meshes] https://mathematica.stackexchange.com/questions/148210/same-region-different-meshes

I’m playing around with ToElementMesh and I noticed the following behaviour that puzzles me. Consider the two regions

&lt;&lt; NDSolve`FEM`

Ω1 =
  Polygon[{{-1/2, -1}, {-1/2, 1}, {1/2, 1}, {1/2,  ...

- asked by Massimo Ortolano (11 votes), answered by user21 (9 votes)

—————————-

[Rearrange the list in a specific way] https://mathematica.stackexchange.com/questions/147876/rearrange-the-list-in-a-specific-way

Suppose I have a list like {"e", "c", "a", "d", "b"} and list of
rules {1 -&gt; 5, 2 -&gt; 3, 3 -&gt; 1, 4 -&gt; 4, 5 -&gt; 2}. The second
list says that for example element on position 1 shoud be on  ...

- asked by David Baghdasaryan (11 votes), answered by Shadowray (16 votes)

—————————-

[Self contained APIFunction. Collecting definitions] https://mathematica.stackexchange.com/questions/148207/self-contained-apifunction-collecting-definitions

Cross posted on community.wolfram.com

Background

After failed attempt (1) to create a complex API, by nicely linking my APIFunction to a cloud based package, I decided to go with the flow and trust ...

- asked by Kuba (10 votes), answered by Leonid Shifrin (4 votes)

—————————-

[Substitute some 1s with 0s in random list] https://mathematica.stackexchange.com/questions/148134/substitute-some-1s-with-0s-in-random-list

How is it better to substitute list of random combination of 1 and 0 (binary image) so that only first (or central) instance of 1 left in each group.

list = 0,1,1,0,0,1,0,1,1,1,0 should be ...

- asked by io_tuta (9 votes), answered by Carl Woll (10 votes)

—————————-

[Pattern matching Association in rules] https://mathematica.stackexchange.com/questions/148074/pattern-matching-association-in-rules

I would appreciate an explanation of how Associations behave in pattern matching, especially when matching rules, and using HoldPattern.

Consider the following:

assocRuleList = {&lt;||&gt; :&gt;  ...

- asked by ZeitPolizei (9 votes), answered by WReach (7 votes)

—————————-

[How to combine Neural Network and Audio like Classify?] https://mathematica.stackexchange.com/questions/148158/how-to-combine-neural-network-and-audio-like-classify

I want to combine Audio object and Neural Network ,first thing I remember is Classify

windInstrument = ExampleData[{"Sound", #}] &amp; /@ {"AltoFlute", "AltoSaxophone", "BassClarinet", "BassFlute",  ...

- asked by partida (8 votes)

—————————-

[ROT13 and upside-down text (flip text)] https://mathematica.stackexchange.com/questions/147829/rot13-and-upside-down-text-flip-text

How can we transform text in order to achieve ROT13 and flip text using Wolfram Mathematica?

1. ROT13

2. Flip text

- asked by rhermans (8 votes), answered by rhermans (11 votes)

================================== Greatest hits from previous weeks: ==================================

[Mathematica 10.0.x freezes in Initializing kernels] https://mathematica.stackexchange.com/questions/92931/mathematica-10-0-x-freezes-in-initializing-kernels

Bug caused by paclet update and fixed by paclet update.

I updated to Windows 10 and have been running Mathematica fine on it for over a month. For some reason, it has just stopped working. I don’t ...

- asked by mitcheljh (73 votes), answered by ilian (94 votes)

—————————-

[1 Plot, 2 Scale/Axis] https://mathematica.stackexchange.com/questions/627/1-plot-2-scale-axis

I would like to plot those two datasets on top of each other. But they have very different range on the y  axis. How can I have two different axis?

I found the following on the help menu but quite ...

- asked by 500 (115 votes), answered by ArgentoSapiens (110 votes)

================================== Can you answer these? ==================================

[How to improve the creation of tables of code and comments] https://mathematica.stackexchange.com/questions/148160/how-to-improve-the-creation-of-tables-of-code-and-comments

While writing a response to a certain MSE question I made a function that tabulates code and comments. (See the definition below.)

Here is an example:

code = "
  FoldList[(* reduction function *)
   ...

- asked by Anton Antonov (5 votes)

—————————-

[Export as HTML: Image of text is squished] https://mathematica.stackexchange.com/questions/147819/export-as-html-image-of-text-is-squished

When exporting a notebook to HTML, the notebook’s cells render as images, but the text is often squished. For example, this notebook:

... renders as

If I manually line-break the code, the ...

- asked by ConvexMartian (3 votes)

—————————-

[How to implement the same function use *Layer function?] https://mathematica.stackexchange.com/questions/148181/how-to-implement-the-same-function-use-layer-function

Reading YOLO method to detect object in the image(paper),I want to train this tiny-VOLO v1 on Mathematica,but the special loss function is very difficult to write.

Total loss is:

For brief,I use ...

- asked by partida (5 votes)

16 Tuesday, June 6, 2017

==================================
Top new questions this week:
==================================

[List of symbols without built-in meaning] https://mathematica.stackexchange.com/questions/147328/list-of-symbols-without-built-in-meaning

Is there a list of all symbols with special display forms but no built-in meaning? That is, operators that are described in the tutorial Operators without Built-in Meanings?

- asked by Carl Woll (17 votes), answered by Carl Woll (17 votes)

—————————-

[Does Mathematica support deep links?] https://mathematica.stackexchange.com/questions/147374/does-mathematica-support-deep-links

So GitHub sent me on quite the journey, after it opened its desktop app from my browser. Copying the link I found something looking like: "github-mac://...". 

I spent the next like 15 minutes trying ...

- asked by b3m2a1 (12 votes), answered by b3m2a1 (12 votes)

—————————-

[How and why to use monadic programming in Mathematica?] https://mathematica.stackexchange.com/questions/147679/how-and-why-to-use-monadic-programming-in-mathematica

This is a methodological question with two parts:

How to use monadic programming in Mathematica?

and Why use monadic programming in Mathematica?

In my opinion the questions are inter-related – ...

- asked by Anton Antonov (10 votes)

—————————-

[Google Drive API connection: (or how can I build a service connection to an OAuth2 service?)] https://mathematica.stackexchange.com/questions/147451/google-drive-api-connection-or-how-can-i-build-a-service-connection-to-an-oaut

From here I know how to build a a basic service connection.

And that’s fine in simple authentication cases but how do I do this for OAuth services?

Even more specifically, how can I do this for ...

- asked by b3m2a1 (10 votes), answered by b3m2a1 (9 votes)

—————————-

[Performance of Nest vs. Do] https://mathematica.stackexchange.com/questions/147545/performance-of-nest-vs-do

When I am iterating the logistic function using a pure function, comparing Do and Nest:

x = 0.1; Do[x = 3 x (1 - x), 300] // RepeatedTiming
Nest[3 # (1 - #) &amp;, .1, 300] // RepeatedTiming

- asked by Stitch (9 votes), answered by Karsten 7. (9 votes)

—————————-

[Huge arrows in 3D graphics] https://mathematica.stackexchange.com/questions/147586/huge-arrows-in-3d-graphics

Hi. Consider the following code:

f1 = Plot3D[-Exp[-x^2-y^2],{x,-5,5},{y,-5,5},PlotRange-&gt;All]
f2 = Graphics3D[Table[{Arrowheads[.01],Arrow[{{2Cos[i],2Sin[i],0},{2.5Cos[i],  ...

- asked by AccidentalFourierTransform (9 votes), answered by Jens (9 votes)

—————————-

[Clean package update for API/FormFunctions on Wolfram Cloud] https://mathematica.stackexchange.com/questions/147330/clean-package-update-for-api-formfunctions-on-wolfram-cloud

Cross posted on community.wolfram.com (new comments)

TLDR

There is a pool of kernels/sessions available for each user, you don’t have control over the pool only over specific kernel you currently ...

- asked by Kuba (7 votes), answered by b3m2a1 (7 votes)

================================== Greatest hits from previous weeks: ==================================

[My Girlfriend is going to prison...Save her with Math] https://mathematica.stackexchange.com/questions/135937/my-girlfriend-is-going-to-prison-save-her-with-math

Salacious title, but true story.

 dmethyl1 = {
      {0, 0},
      {.25, 1},
      {.5, 7},
      {1, 26},
      {1.5, 40},
      {2, 45},
      {2.5, 45},
      {3, 44},
      {3.5, 44},
      {4,  ...

- asked by Prisoners Dilema (37 votes), answered by bobthechemist (24 votes)

—————————-

[Creating legends for plots with multiple lines?] https://mathematica.stackexchange.com/questions/4025/creating-legends-for-plots-with-multiple-lines

So I have a graph with multiple lists, for e.g.

data = {{1,2}, {3,4}, {3,5}, {2,3} . . .}


If I then do ListLinePlot[Table[{#1,Log[b,#2]}&amp;@@@data, {b,1,10,2}]] I have no way to generate a legend  ...

- asked by Eiyrioü von Kauyf (60 votes), answered by Jens (89 votes)

================================== Can you answer these? ==================================

[URLFetch parameters interfere with POST] https://mathematica.stackexchange.com/questions/147526/urlfetch-parameters-interfere-with-post

(orig: URLFetch Multipart POST fails to post Body?)

Update 2:

So after much weeping and gnashing of teeth our Lord and Savior Mathematica deemed me worthy of figuring out (some of) what the hell was ...

- asked by b3m2a1 (1 vote)

—————————-

[What is the best method for solving D (a,b,r,t)  under a 5-minute computation time?] https://mathematica.stackexchange.com/questions/147520/what-is-the-best-method-for-solving-da-b-r-t-under-a-5-minute-computation-ti

Consider set {T (c,d)|c,d ∈ ℤ} , a subset of rational numbers, where T(c,d)  is a function.

I want to compute D (a,b,r,t)

...

- asked by Arbuja (1 vote)

—————————-

[Loop construction with multiple expressions for solving differential equation] https://mathematica.stackexchange.com/questions/147523/loop-construction-with-multiple-expressions-for-solving-differential-equation

I want to solve the following ODE.

  ′′  2  ′  ∂Veff(H,r)
H   + rH  −    ∂H    =  0

with the following conditions

ddHr (r = 0) = 0  and H (r = ∞ ) = 0

Regardless of the ...

- asked by Konstantinos (2 votes)

17 Tuesday, May 30, 2017

==================================
Top new questions this week:
==================================

[Estimate the ”Blurry” distribution of an image] https://mathematica.stackexchange.com/questions/146989/estimate-the-blurry-distribution-of-an-image

I’m trying to analyze an image obtained by scanning electron microscope(SEM) where different parts of the same image has has different blurring radius. My goal is to determine how blurry different ...

- asked by Wjx (17 votes), answered by Shadowray (20 votes)

—————————-

[Nest list with two functions] https://mathematica.stackexchange.com/questions/147055/nest-list-with-two-functions

Is it possible to use the NestList command with two functions, one at every even step and apply the other at every odd step. If this is possible could someone share an example ?

- asked by David (12 votes), answered by Shadowray (14 votes)

—————————-

[Exporting structured data to HDF5] https://mathematica.stackexchange.com/questions/146859/exporting-structured-data-to-hdf5

Sadly the documentation is lacking any useful examples on how to Export more complex data in HDF5. There is only

  Export["file.h5",{expr1,...},{"Datasets", {"dataset1",...}}] creates an HDF5 file,  ...

- asked by Sascha (10 votes), answered by Sascha (5 votes)

—————————-

[Using Mathematica to create an H-Tree] https://mathematica.stackexchange.com/questions/146797/using-mathematica-to-create-an-h-tree

Can folks show me several methods I can use to draw the following fractal H-Tree?

I did use Free-Form input, as:

= h-fractal

And got this image, which is three iterations, but no idea how it was ...

- asked by David (10 votes), answered by J. M. (10 votes)

—————————-

[Combining # & pure functions with post-fix notation] https://mathematica.stackexchange.com/questions/147132/combining-pure-functions-with-post-fix-notation

I can’t find the link anymore but there was a talk at a Wolfram conference (referencing v7 I think) where the authors highlight that stringing together functions like this:

Range[100] //  ...

- asked by Joe (9 votes), answered by Szabolcs (7 votes)

—————————-

[Hosting a curated data function / server in Google Drive] https://mathematica.stackexchange.com/questions/146832/hosting-a-curated-data-function-server-in-google-drive

I want to make a curated data function, but I have no good place to store the paclets.

Per the pricing page I only get:

And that’s really not enough to host all of my data plus give me room to do ...

- asked by MB1965 (9 votes), answered by MB1965 (8 votes)

—————————-

[Interpolate the noisy data] https://mathematica.stackexchange.com/questions/146688/interpolate-the-noisy-data

I have some noisy data

data = Uncompress[FromCharacterCode[
   Flatten[ImageData[Import["http://i.stack.imgur.com/RZcpj.png"],"Byte"]]]]

Plot looks like this

There is noise in certain region, ...

- asked by Saesun Kim (9 votes), answered by bill s (8 votes)

================================== Greatest hits from previous weeks: ==================================

[Creating Mathematica packages] https://mathematica.stackexchange.com/questions/29324/creating-mathematica-packages

I’m building a package to help me write packages and their documentation. In this post I explained how to make a package and its documentation. In the answer I provided I describe how to build a very ...

- asked by jmlopez (89 votes), answered by Leonid Shifrin (114 votes)

—————————-

[How can I plot the direction field for a differential equation?] https://mathematica.stackexchange.com/questions/8841/how-can-i-plot-the-direction-field-for-a-differential-equation

I’d like to plot the graph of the direction field for a differential equation, to get a feel for it. I’m a novice, right now, when it comes to plotting in Mathematica, so I’m hoping that someone can ...

- asked by Matt Groff (20 votes), answered by Peter Breitfeld (17 votes)

================================== Can you answer these? ==================================

[How to replace all instances of a number throughout my entire cell] https://mathematica.stackexchange.com/questions/146971/how-to-replace-all-instances-of-a-number-throughout-my-entire-cell

I have a cell where for several instances throughout I label certain functions, strings, and ranges using a similar pattern so as to follow through with integration calculations, list forming, and ...

- asked by yalev (3 votes)

—————————-

[Error occurred while connecting to remote kernel.Can’t use dynamic] https://mathematica.stackexchange.com/questions/146823/error-occurred-while-connecting-to-remote-kernel-cant-use-dynamic

When Open Mathematica using remote kernel,it throws LinkConnect error.
But normal command can evaluate.Like Range@5,$Version...

But Cant use dynamic.It throws An unknown box name.
So if I want to  ...

- asked by partida (4 votes)

—————————-

[Partition an Image automatically Based on Borders] https://mathematica.stackexchange.com/questions/146837/partition-an-image-automatically-based-on-borders

I would like to be able to train a model to recognize the borders in a newspaper image and then partition those into separate Images. Images similar to this would be the input Image

And then ...

- asked by Avadhut Bhosarekar (2 votes)

18 Tuesday, May 23, 2017

==================================
Top new questions this week:
==================================

[PerformanceGoal option ignored in V11.1] https://mathematica.stackexchange.com/questions/146214/performancegoal-option-ignored-in-v11-1

Bug introduced in 11.1

[CASE:3892079] was created

[...] I have reproduced this problem with PerformanceGoal in version 11.1 and reported the issue to our developers [...]

Take this code:

...

- asked by Kuba (14 votes), answered by Kuba (15 votes)

—————————-

[Can I build my own curated data function?] https://mathematica.stackexchange.com/questions/146220/can-i-build-my-own-curated-data-function

I love the huge curated datasets, but they don’t cover everything. I have my own huge dataset which is too much to distribute as an EntityStore so is there a way to build my own analog of, say, ...

- asked by MB1965 (13 votes), answered by MB1965 (16 votes)

—————————-

[Support for low-complexity (compressible) lists] https://mathematica.stackexchange.com/questions/146244/support-for-low-complexity-compressible-lists

By ”low-complexity list” I mean a list like the following:

lcl = {17, 17, 17, 17, 17,
       21, 21, 21, 21, 21, 21, 21, 21,
       11, 11, 11, 11, 11, 11, 11}

It contains 20 elements, but only 3 ...

- asked by kjo (10 votes), answered by Mr.Wizard (6 votes)

—————————-

[Automating documentation generation] https://mathematica.stackexchange.com/questions/146670/automating-documentation-generation

Outside of kernel symbols Mathematica provides access to lots of usage info, e.g. DownValues, Options, Messages, etc.

Most languages, if given this sort of info, would be able to provide an automatic ...

- asked by MB1965 (9 votes), answered by MB1965 (10 votes)

—————————-

[Trace of -1 expression] https://mathematica.stackexchange.com/questions/146506/trace-of-1-expression

I’m trying to understand Trace. Usually it doesn’t repeat but it adds -1,-1 for his simple expression after having a correct result.

-{1}//Trace

  {-1, {-1}, {-1, -1}, {-1}}


Why -{1}//Trace is  ...

- asked by io_tuta (9 votes), answered by Michael E2 (7 votes)

—————————-

[How to import a Tensorflow model?] https://mathematica.stackexchange.com/questions/146216/how-to-import-a-tensorflow-model

I’ve trained a network in Tensorflow and have the checkpoint files, I’d like to if anyone has written a parser or importer to pull the evaluation graph and/or weights into Mathematica?

- asked by user5601 (9 votes)

—————————-

[intersection between two 2D arrays with labeled data is slow] https://mathematica.stackexchange.com/questions/146558/intersection-between-two-2d-arrays-with-labeled-data-is-slow

Here is how to Generate data

the function is below with two images to generate data

img1

img2


segmentImage[binarizedMask_?ImageQ] :=
Module[{seg, areas, indexMaxarea, maxArea},
seg =  ...

- asked by Ali Hashmi (8 votes), answered by Carl Woll (6 votes)

================================== Greatest hits from previous weeks: ==================================

[Exporting graphics to PDF - huge file] https://mathematica.stackexchange.com/questions/1542/exporting-graphics-to-pdf-huge-file

I want to draw some basic surfaces, export them to PDF and include them in a LaTeX file. I create a simple 3D graphics object, for instance with

 ParametricPlot3D[{r Cos[θ], r Sin[θ], r^2}, {r, 0,  ...

- asked by Matthew Leingang (92 votes), answered by Heike (80 votes)

—————————-

[Generating a Sierpinski carpet] https://mathematica.stackexchange.com/questions/22052/generating-a-sierpinski-carpet

I am trying to draw a Sierpinski_carpet. I have code that works, but I think there is a more elegant way to do than my way. Maybe I couls use Tuples or Permutations or some similar function to ...

- asked by chyaong (46 votes), answered by Mr.Wizard (75 votes)

================================== Can you answer these? ==================================

[Exporting graphics with VertexColors problem] https://mathematica.stackexchange.com/questions/146306/exporting-graphics-with-vertexcolors-problem

I’ve generated a graphics which exhibit gradient color in rectangle and export it as:

SetDirectory[NotebookDirectory[]];
Export["./test.pdf", Graphics[{Polygon[{{-4, 5/3}, {-4, 0}, {4, 0}, {4,  ...

- asked by RoderickLee (3 votes)

—————————-

[How to imitate the opacity plot in EditColorFunction] https://mathematica.stackexchange.com/questions/146623/how-to-imitate-the-opacity-plot-in-editcolorfunction

I wish to imitate the opacity plot as shown below:

Edit2: (ref: https://www.wolfram.com/mathematica/new-in-9/3d-volumetric-image-processing/edit-color-function-palette-for-image3d.html)

Here is ...

- asked by Majis (3 votes)

—————————-

[Possible bug in Export with CharacterEncoding -¿ ”PrintableASCII”] https://mathematica.stackexchange.com/questions/146294/possible-bug-in-export-with-characterencoding-printableascii

In the Documentation we read (emphasis is mine):

By default, the Wolfram System uses the character encoding ”PrintableASCII” when saving notebooks and packages. This means that when special ...

- asked by Alexey Popkov (4 votes)

19 Tuesday, May 16, 2017

==================================
Top new questions this week:
==================================

[Mathematica stuck in ”running” for every calculation I attempt, kernel error] https://mathematica.stackexchange.com/questions/146005/mathematica-stuck-in-running-for-every-calculation-i-attempt-kernel-error

Bug caused by paclet update and fixed by paclet update.

I downloaded Mathematica this morning to do an implicit polar plot. I attempt to run the code

Manipulate[
ContourPlot[
Evaluate@With[{r =  ...

- asked by 0celouvskyopoulo7 (26 votes), answered by ilian (16 votes)

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[How to split data into clusters based on fitting to function] https://mathematica.stackexchange.com/questions/146079/how-to-split-data-into-clusters-based-on-fitting-to-function

I have data which looks somewhat like this:

On the picture, you can see that the data can be described by 2 linear functions - if you manage to split it into 2 groups, each can easily be fitted ...

- asked by Arsen Zahray (10 votes), answered by rhermans (11 votes)

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[Inserting cones at intersection points two curves] https://mathematica.stackexchange.com/questions/145874/inserting-cones-at-intersection-points-two-curves

I am plotting the null geodesics for a Schwarzschild surface in Schwarzschild coordinates and would light to insert small future light-cones at the points of intersection to emphasize the tipping over ...

- asked by Soof_fie (9 votes), answered by rhermans (3 votes)

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[How to define a function inside a Compile?] https://mathematica.stackexchange.com/questions/145931/how-to-define-a-function-inside-a-compile

I want to compile a variety of commands, including a function. I need to map this function, inside the compilation, and I can’t include the function without facing errors such as ...

- asked by user5253864 (9 votes), answered by xzczd (10 votes)

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[How to automatically do a computation, Quit[], restart and do a new computation] https://mathematica.stackexchange.com/questions/145852/how-to-automatically-do-a-computation-quit-restart-and-do-a-new-computation

Related questions have been asked before (eg Where does a package have to be loaded?, http://stackoverflow.com/questions/6152023/quit-kernel-in-mathematica-by-a-command-not-using-evaluation-menu

- asked by Gaius (9 votes), answered by Shadowray (6 votes)

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[1D transient heat equation problem with controller] https://mathematica.stackexchange.com/questions/145799/1d-transient-heat-equation-problem-with-controller

I would appreciate some help with following issue:

I am trying to solve a 1D transient heat equation problem with a control loop in order to compensate a time variable boundary condition at one ...

- asked by daklems (9 votes), answered by user21 (6 votes)

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[Clarify when to use Style vs Directive vs List] https://mathematica.stackexchange.com/questions/145856/clarify-when-to-use-style-vs-directive-vs-list

I am confused about when to use a simple list of style options, the Directive function or the Style function.

As shown below, for simple situations at least, they seem entirely equivalent which ...

- asked by Joe (8 votes)

================================== Greatest hits from previous weeks: ==================================

[How to manipulate 2D plots?] https://mathematica.stackexchange.com/questions/7142/how-to-manipulate-2d-plots

When it comes to visual analysis, large datasets or data with intricate internal details often makes plotting in 2D useless, as the outcome is either just a fraction of the full dataset, or no details ...

- asked by István Zachar (115 votes), answered by István Zachar (131 votes)

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[Where can I find examples of good Mathematica programming practice?] https://mathematica.stackexchange.com/questions/18/where-can-i-find-examples-of-good-mathematica-programming-practice

I consider myself a pretty good Mathematica programmer, but I’m always looking out for ways to either improve my way of doing things in Mathematica, or to see if there’s something nifty that I haven’t ...

- asked by J. M. (463 votes), answered by faysou (411 votes)

================================== Can you answer these? ==================================

[Unexpected behavior of a variable] https://mathematica.stackexchange.com/questions/145661/unexpected-behavior-of-a-variable

I am confused with a strange phenomenon that I observe and do not understand.

Look, here is a simple code making a random walk:

Clear[list];
list = Accumulate[RandomInteger[{-1, 1}, {10, 2}]]

- asked by Alexei Boulbitch (2 votes)

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[How can I disable system updates only?] https://mathematica.stackexchange.com/questions/146133/how-can-i-disable-system-updates-only

Suppose I’m quite happy with my current Mathematica installation and wish to keep the system in its current form just reliably working.

Since there were already at least two cases[1,2] when a lot of ...

- asked by Alexey Popkov (7 votes)

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[Import/export manipulate state in file] https://mathematica.stackexchange.com/questions/146017/import-export-manipulate-state-in-file

Is it possible to export the state of Manipulate with big number of parameters in file and then restore the parameters of Manipulate from this file?

- asked by Филипп Цветков (3 votes)

20 Tuesday, May 2, 2017

==================================
Top new questions this week:
==================================

[Count works differently depending on how an association was created] https://mathematica.stackexchange.com/questions/144813/count-works-differently-depending-on-how-an-association-was-created

Bug introduced in 10.4 and persisting through 11.1.1

I create two associations, that are supposed to be exactly the same. And then I want to count the elements at the second level. And I get ...

- asked by Stitch (19 votes), answered by WReach (12 votes)

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[Why is Plus so much slower than Total?] https://mathematica.stackexchange.com/questions/145019/why-is-plus-so-much-slower-than-total

Why is Plus so much slower than total for summing lists?

list = RandomReal[1, 10000000];
AbsoluteTiming[Plus @@ list]
AbsoluteTiming[Total[list]]


Output:

{1.67408, 5.00073*10^6}
{0.00570379,  ...

- asked by Jorge Perez (14 votes), answered by Shadowray (17 votes)

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[Delete duplicates from list of lists as if on a necklace] https://mathematica.stackexchange.com/questions/144696/delete-duplicates-from-list-of-lists-as-if-on-a-necklace

Given a list of lists of integers, all of the same length, I want to regard two elements as equivalent if one is the rotated and/or reflected version of another (that is, if the two lists are the same ...

- asked by rogerl (13 votes), answered by Shadowray (13 votes)

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[Exchanging numpy arrays between Python and Mathematica?] https://mathematica.stackexchange.com/questions/144770/exchanging-numpy-arrays-between-python-and-mathematica

Ive been using np.savetxt(location, result, delimiter=,)
in Python followed by Import[location,"CSV"] in Mathematica.
 Some of my files are around 1GB, opening seems a bit slow, what else do people  ...

- asked by Yaroslav Bulatov (12 votes), answered by xslittlegrass (16 votes)

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[How to plot planar graphs in a visually pleasing way?] https://mathematica.stackexchange.com/questions/144594/how-to-plot-planar-graphs-in-a-visually-pleasing-way

Cross posted to Wolfram Community

Mathematica has a layout algorithm to plot planar graphs without edge crossings. This typically produces an ugly triangular layout where some vertices and edges ...

- asked by Szabolcs (11 votes), answered by Szabolcs (6 votes)

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[Where are my Cloud Credits going?] https://mathematica.stackexchange.com/questions/144859/where-are-my-cloud-credits-going

In less than a month Ive used 5k cloud credits (half of my quota)
and all I did was deploying a bunch of static notebooks with
CloudDeploy[CurrentNotebook[],permissions-&gt;Public] (more  ...

- asked by Yaroslav Bulatov (10 votes)

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[Mathematica erroneously says this integral does not converge] https://mathematica.stackexchange.com/questions/144965/mathematica-erroneously-says-this-integral-does-not-converge

Mathematica (as of v. 11.1.0) does not recognize that this special case of Frullani’s integral converges:

Integrate[(ArcTan[a*x] - ArcTan[b*x])/x, {x, 0, Infinity}]
(* Integrate::idiv: Integral of  ...

- asked by Pillsy (10 votes), answered by Michael E2 (16 votes)

================================== Greatest hits from previous weeks: ==================================

[Generating a Sierpinski carpet] https://mathematica.stackexchange.com/questions/22052/generating-a-sierpinski-carpet

I am trying to draw a Sierpinski_carpet. I have code that works, but I think there is a more elegant way to do than my way. Maybe I couls use Tuples or Permutations or some similar function to ...

- asked by chyaong (46 votes), answered by Mr.Wizard (75 votes)

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[Alternatives to procedural loops and iterating over lists in Mathematica] https://mathematica.stackexchange.com/questions/7924/alternatives-to-procedural-loops-and-iterating-over-lists-in-mathematica

While there are some cases where a For loop might be reasonable, it’s a general mantra – one I subscribe to myself – that ”if you are using a For loop in Mathematica, you are probably doing it wrong”. ...

- asked by Mr.Wizard (154 votes), answered by Mr.Wizard (104 votes)

================================== Can you answer these? ==================================

[How to get parent key in Query on Association/Dataset?] https://mathematica.stackexchange.com/questions/144995/how-to-get-parent-key-in-query-on-association-dataset

Is there a general and terse method to obtain the parent key of the current ”position” in a Query of an Association/Dataset?

Say I have the following Association.

assoc =
 &lt;|"A" -&gt;
     ...

- asked by Edmund (3 votes)

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[Can anyone help me decipher these few lines? Also, converting this code for a 2x2 matrix input to a 3x3 matrix input?] https://mathematica.stackexchange.com/questions/145049/can-anyone-help-me-decipher-these-few-lines-also-converting-this-code-for-a-2x

Here’s the code. I’m completely new to Mathematica so bear with me.

clear[ug];
ug[{{a11_, a12_}, {a21_, a22_}}] :=
 Module[{A, f, b1, b2, y1, y2, U, P1, P2, UG},
  A = {{a11, a12}, {a21, a22}};
   ...

- asked by Pacotacobell (2 votes)

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[Bifurcation package like AUTO?] https://mathematica.stackexchange.com/questions/144795/bifurcation-package-like-auto

I was wondering if there is any available continuation and bifurcation analysis package for Mathematica. I’m looking for something like AUTO. I’ve seen there is already a Matlab version of the ...

- asked by Mirko Aveta (3 votes)

21 Tuesday, April 25, 2017

==================================
Top new questions this week:
==================================

[Fast spherical polygon] https://mathematica.stackexchange.com/questions/144167/fast-spherical-polygon

Cross posted on Wolfram Community

Question

Given a list of points on a sphere and the sphere’s radius, I’d like to plot a spherical polygon with those points as vertices.

And this needs to be fast, ...

- asked by Kuba (20 votes), answered by halirutan (7 votes)

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[How to uncompress strings safely (without any evaluation)?] https://mathematica.stackexchange.com/questions/144171/how-to-uncompress-strings-safely-without-any-evaluation

Compressed strings are often used to exchange Mathematica expressions on the Internet. It is, however, not easy to see what such expression will do after decompression. Resulting code can perform ...

- asked by Shadowray (15 votes), answered by Itai Seggev (11 votes)

—————————-

[Sharing data via the cloud] https://mathematica.stackexchange.com/questions/144130/sharing-data-via-the-cloud

I’ve got some stuff that I want to be able distribute to my totally real friends, but I don’t want to have to email them every time I change something.

How can I set up sharing via the cloud?

- asked by MB1965 (13 votes), answered by MB1965 (13 votes)

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[C++ interface to large project] https://mathematica.stackexchange.com/questions/144047/c-interface-to-large-project

We are developing a quite large mathematical software in C++ and would like to have a Mathematica interface. We have our own C++ library and our idea would be, to write a Mathematica wrapper class and ...

- asked by Richard (12 votes), answered by Szabolcs (12 votes)

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[Why doesn’t FullSimplify return -x working on Abs[x] and x¡0?] https://mathematica.stackexchange.com/questions/144310/why-doesnt-fullsimplify-return-x-working-on-absx-and-x0

I am using Mathematica 11.1, and I stumbled upon this strange response using the Abs function.

FullSimplify[Abs[x],x&lt;0]
(* Abs[x] *)


while, for example

FullSimplify[Abs[x],x&gt;0]
(* x *)

as ...

- asked by mickep (10 votes), answered by Simon Woods (13 votes)

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[ParallelMap vs Map performance comparsion] https://mathematica.stackexchange.com/questions/144056/parallelmap-vs-map-performance-comparsion

The ParallelMap claims doing map faster than the normal Map, and I checked the demo does as the document describing

but, I try my testing, it seems not exactly while ParallelMap excuting with 8 ...

- asked by Jerry (10 votes), answered by Szabolcs (10 votes)

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[How to plot a matrix with 3D style] https://mathematica.stackexchange.com/questions/144443/how-to-plot-a-matrix-with-3d-style

I have a list like

SeedRandom[1]
MatrixForm[list = RandomInteger[5, {5, 5}]]

We can plot it with MatrixPlot directly with 2D style

MatrixPlot[list]

I hope to plot it with 3D style.This is ...

- asked by yode (9 votes), answered by kglr (2 votes)

================================== Greatest hits from previous weeks: ==================================

[Where can I find examples of good Mathematica programming practice?] https://mathematica.stackexchange.com/questions/18/where-can-i-find-examples-of-good-mathematica-programming-practice

I consider myself a pretty good Mathematica programmer, but I’m always looking out for ways to either improve my way of doing things in Mathematica, or to see if there’s something nifty that I haven’t ...

- asked by J. M. (463 votes), answered by faysou (410 votes)

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[How can I plot the direction field for a differential equation?] https://mathematica.stackexchange.com/questions/8841/how-can-i-plot-the-direction-field-for-a-differential-equation

I’d like to plot the graph of the direction field for a differential equation, to get a feel for it. I’m a novice, right now, when it comes to plotting in Mathematica, so I’m hoping that someone can ...

- asked by Matt Groff (20 votes), answered by Peter Breitfeld (16 votes)

================================== Can you answer these? ==================================

[Quality of RegionIntersection[]: How to control?] https://mathematica.stackexchange.com/questions/144270/quality-of-regionintersection-how-to-control

This code produces a crude intersection.

a = {-1/2, -1/2, -1/2};
b = {1/2, 1/2, 1/2};
R = RegionIntersection[Ball[a, 1], Ball[b, 1]];
Region[R]

How can I control the quality so that the ...

- asked by Joseph O’Rourke (4 votes)

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[Why ReadList ignores NullRecords for Number?] https://mathematica.stackexchange.com/questions/144149/why-readlist-ignores-nullrecords-for-number

When thinking on this recent question the immediately obvious
solution which came to my mind was to use ReadList with options
RecordLists -&gt; True and NullRecords -&gt; True for reading objects of  ...

- asked by Alexey Popkov (5 votes)

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[Why does the domain of an interpolating function not match the corresponding ParametricNDSolve solution range?] https://mathematica.stackexchange.com/questions/144355/why-does-the-domain-of-an-interpolating-function-not-match-the-corresponding-par

Question

I had believed - and mostly observed - that when I use ParametricNDSolve the obtained ParametricFunctions given as the solution to some ODE or DAE will be translated into ...

- asked by gwr (3 votes)

22 Tuesday, April 18, 2017

==================================
Top new questions this week:
==================================

[Crack CAPTCHA using deep learning] https://mathematica.stackexchange.com/questions/143691/crack-captcha-using-deep-learning

Deep convolutional neural networks are very good at computer vision related tasks. Optical Character Recognition (OCR) is one important branch of computer vision. In fact, the convolution neural ...

- asked by xslittlegrass (50 votes), answered by xslittlegrass (52 votes)

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[Changes to Series[...] in version 11.1] https://mathematica.stackexchange.com/questions/143414/changes-to-series-in-version-11-1

I have updated to Mathematica 11.1 and I am shocked to see that the Series-function now works differently:

If I enter

Series[x^2+x^3, {x,0,0}]


it will return

x^2+O[x]^3

which is just weird. In ...

- asked by Matthias Koenig (16 votes), answered by QuantumDot (3 votes)

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[WLNet format incompatible between version 11.0 and 11.1] https://mathematica.stackexchange.com/questions/143699/wlnet-format-incompatible-between-version-11-0-and-11-1

It seems that there are some behavior changes of neural network layers from version 11.0 to 11.1 that leads to the incompatibility of WLNet format.

Consider this example:

Network exported in 11.0

...

- asked by xslittlegrass (13 votes), answered by Taliesin Beynon (7 votes)

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[DSolve solution depends on ordering of equation] https://mathematica.stackexchange.com/questions/143726/dsolve-solution-depends-on-ordering-of-equation

Bug introduced in 8.0 or earlier and persisting through 11.1.0 or later

I am trying to obtain the general solution, G (x1,x2,x3,x4 )  to the very easy system of PDEs:

- asked by Jeremy Upsal (12 votes), answered by Nasser (8 votes)

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[Why the Callout option makes plotting performance poor] https://mathematica.stackexchange.com/questions/143711/why-the-callout-option-makes-plotting-performance-poor

Bug introduced in 11.0 and fixed in 11.1

The Callout option is a new option for plotting, but the performance is very poor, see bellow testing case.

num = 1000;
list = N@Sin@Range[num];
list2 =  ...

- asked by Jerry (11 votes)

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[Neural machine translation model using deep learning] https://mathematica.stackexchange.com/questions/143609/neural-machine-translation-model-using-deep-learning

In Mathematica version 11.1, SequenceAttentionLayer is introduced to model attentions in the recurrent neural network. It has been shown that attention mechanism can greatly improve the quality of a ...

- asked by xslittlegrass (11 votes), answered by Sebastian (8 votes)

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[Backslide in NSolve in V11.1?] https://mathematica.stackexchange.com/questions/143824/backslide-in-nsolve-in-v11-1

In V11.1,

NSolve[BesselJ[0, x] == 0 &amp;&amp; 0 &lt; x &lt; 20, x]

returns no solutions:

But in V11.0 (and earlier), it returns all solutions:

Is there anyway to get NSolve to solve this ...

- asked by Michael E2 (10 votes), answered by Nasser (8 votes)

================================== Greatest hits from previous weeks: ==================================

[How to perform a multi-peak fitting?] https://mathematica.stackexchange.com/questions/26336/how-to-perform-a-multi-peak-fitting

I am wondering how to implement the multi-peak detecting and fitting in Mathematica. Following is an example of fitting the data using three peaks (such that the data   peak1 + peak2 + peak3).

The ...

- asked by Everett You (43 votes), answered by Silvia (45 votes)

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[How to make an inkblot?] https://mathematica.stackexchange.com/questions/3345/how-to-make-an-inkblot

How to effectively create a polygon that looks like a realistic inkblot? So far, I could come up with this (borrowing from Ed Pegg Jr.’s Rorschach demonstration):

RandomBlot[num_, opts___] :=  ...

- asked by István Zachar (84 votes), answered by Sjoerd C. de Vries (47 votes)

================================== Can you answer these? ==================================

[How to create an APIFunction that takes a list with constraints on the list elements?] https://mathematica.stackexchange.com/questions/143709/how-to-create-an-apifunction-that-takes-a-list-with-constraints-on-the-list-elem

This APIFunction takes a list as an argument:

func = APIFunction[{"x" -&gt; DelimitedSequence["Integer", ","]}, #x^3 &amp;]

func["x" -&gt; Range[4]]

What I’d like to be able to do is place a ...

- asked by Mike Honeychurch (4 votes)

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[How to setup FrameTicks for TradingChart] https://mathematica.stackexchange.com/questions/143705/how-to-setup-frameticks-for-tradingchart

I’m trying to setup FrameTicks for TradingChart, but it dosn’t work.

(*take data*)
data = FinancialData["NASDAQ:AAPL", "OHLCV", {{2017, 1, 1}, {2017, 4, 16}}];

(*def. of ticks*)
maxh =  ...

- asked by Jerry (3 votes)

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[What are the software requirements to train neural networks on GPU?] https://mathematica.stackexchange.com/questions/143795/what-are-the-software-requirements-to-train-neural-networks-on-gpu

It seems that GPU training in Mathematica has some additional requirements on the software. For example, when I run this example on a Linux system, I get the following errors

trainingData =
   ...

- asked by xslittlegrass (8 votes)

23 Tuesday, April 11, 2017

==================================
Top new questions this week:
==================================

[L-System in Mathematica] http://mathematica.stackexchange.com/questions/143214/l-system-in-mathematica

Here is some Maple code for drawing an L-System:

  with(Fractals:-LSystem)
  cons := ["A" = "draw:1", "+" = "turn:-90", "B" = "turn:90"]
  state, rules := "A", ["A" = "AB+BA+B", "B" = "B+AAB"]
   ...

- asked by vito (21 votes), answered by Szabolcs (21 votes)

—————————-

[What’s purpose of the new function BinarySerialize?] http://mathematica.stackexchange.com/questions/141885/whats-purpose-of-the-new-function-binaryserialize

11.1 introduced a new function BinarySerialize, but I don’t know what it can do better than the traditional method.Its behavior is very similar to Compress,though I cannot find any advantage of it.It ...

- asked by yode (17 votes), answered by Shadowray (14 votes)

—————————-

[Why does SetPrecision not apply to 0?] http://mathematica.stackexchange.com/questions/143296/why-does-setprecision-not-apply-to-0

Is there a rationale why SetPrecision works on integers except for 0?

SetPrecision[1,5]

  1.0000


SetPrecision[0,5]

  0

- asked by alancalvitti (11 votes), answered by Shadowray (17 votes)

—————————-

[How to use Mathematica to train a network Using out of core classification?] http://mathematica.stackexchange.com/questions/142135/how-to-use-mathematica-to-train-a-network-using-out-of-core-classification

I see there is doc about how to train a network Using out of core image classification and this question.But the object is only image.

I want to use a binary file as data,for example,this.

data = ...

- asked by partida (10 votes), answered by xslittlegrass (9 votes)

—————————-

[Combining pure functions] http://mathematica.stackexchange.com/questions/142072/combining-pure-functions

Is there an easy way to combine pure functions into a single pure function? For example, say I have

f = #1^2 &amp;;
g = #1 - 2 &amp;;

and I want to define a new pure function h that is the ...

- asked by tparker (10 votes), answered by Kuba (5 votes)

—————————-

[Question about changes in Documentation Center from version 10 to 11] http://mathematica.stackexchange.com/questions/143335/question-about-changes-in-documentation-center-from-version-10-to-11

The package Exploring Abstract Algebra with Mathematica works fine in Mathematica 10.4.

After installing it in the $UserBaseDirectory it neatly shows up under Add-Ons and Packages in the ...

- asked by nilo de roock (9 votes), answered by Szabolcs (8 votes)

—————————-

[How can I install packages distributed as .paclet files?] http://mathematica.stackexchange.com/questions/141887/how-can-i-install-packages-distributed-as-paclet-files

I downloaded a Mathematica package. It came as a file with the .paclet extension. How can I install or uninstall it?

- asked by Szabolcs (9 votes), answered by Szabolcs (8 votes)

================================== Greatest hits from previous weeks: ==================================

[Exporting graphics to PDF - huge file] http://mathematica.stackexchange.com/questions/1542/exporting-graphics-to-pdf-huge-file

I want to draw some basic surfaces, export them to PDF and include them in a LaTeX file. I create a simple 3D graphics object, for instance with

 ParametricPlot3D[{r Cos[θ], r Sin[θ], r^2}, {r, 0,  ...

- asked by Matthew Leingang (90 votes), answered by Heike (77 votes)

—————————-

[Unit Discovery: Is this some sort of a sick joke?] http://mathematica.stackexchange.com/questions/124745/unit-discovery-is-this-some-sort-of-a-sick-joke

Alright, let’s have some fun here. I am essentially following the documentation by Wolfram, just looking at different quantities.

N[UnitConvert[Quantity["earths gravity"]]]

9.80665m/(s)^2


Hmm,  ...

- asked by Pirx (31 votes), answered by user31159 (30 votes)

================================== Can you answer these? ==================================

[How to get consistent/predictable results from ‘Alignment‘ specs within a ‘Grid‘ environment?] http://mathematica.stackexchange.com/questions/142047/how-to-get-consistent-predictable-results-from-alignment-specs-within-a-grid

IME, the results of Alignment specifications within a Grid environment are completely unpredictable.

I give several examples below illustrating this unpredictability.

My questions are:

Is there a ...

- asked by kjo (4 votes)

—————————-

[Why Integrate does not work in the first call?] http://mathematica.stackexchange.com/questions/143199/why-integrate-does-not-work-in-the-first-call

Consider an example (calculated in Mathematica 11.0.1.0):

In[1]:= Integrate[(Sin[(\[Pi] xc)/(2 Lc)] Sin[(m \[Pi]  ...

- asked by Shinrei (3 votes)

—————————-

[Geo data load issues: Texas is missing from GeoRegionValuePlot in v11, but only when mapping US states] http://mathematica.stackexchange.com/questions/142079/geo-data-load-issues-texas-is-missing-from-georegionvalueplot-in-v11-but-only

UPDATE: this is not a global Mathematica issue, but a data load issue on a local machine. Does anyone know how to clear Geo cache and reload the data? I’ve also noticed on this machine that ...

- asked by Gregory Klopper (3 votes)

24 Tuesday, April 4, 2017

==================================
Top new questions this week:
==================================

[Object detection and localization using neural network] http://mathematica.stackexchange.com/questions/141598/object-detection-and-localization-using-neural-network

Four important computer vision tasks are classification, localization, object detection and instance segmentation (image taken from cs224d course):

These four tasks are all built on top of the deep ...

- asked by xslittlegrass (30 votes), answered by xslittlegrass (33 votes)

—————————-

[Ball Bouncing on Hilly Terrain] http://mathematica.stackexchange.com/questions/141209/ball-bouncing-on-hilly-terrain

There is a maple code for the bouncing ball on the given curve.

I tried to make this animation by using Mathematica

Why does the following code not work?

surf := Sin[x] + (0.2 Cos[4 x + Sin[4  ...

- asked by vito (19 votes), answered by Stitch (15 votes)

—————————-

[Dataset is 20X slow when adding column heads] http://mathematica.stackexchange.com/questions/141223/dataset-is-20x-slow-when-adding-column-heads

I’m trying to use Dataset to explore some large data. I notice that the performance decrease more than 20X by adding heads to the columns. Here is an example:

We generate some data with integers

...

- asked by xslittlegrass (14 votes), answered by Mr.Wizard (3 votes)

—————————-

[Benchmarking: unexplained switching between high and low performance] http://mathematica.stackexchange.com/questions/141350/benchmarking-unexplained-switching-between-high-and-low-performance

tl;dr I am trying to accurately benchmark some vectorized operations, and compare them between systems. But benchmarking is hard to do well, and I am getting inconsistent results: performance is ...

- asked by Szabolcs (13 votes)

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[How to visualize attention?] http://mathematica.stackexchange.com/questions/141542/how-to-visualize-attention

In the articles about sequence attention we can see images like this:

Here we see that while translating from French to English, the network attends sequentially to each input state, but sometimes ...

- asked by Alexey Golyshev (12 votes), answered by xslittlegrass (4 votes)

—————————-

[Can one create a custom front-end for Mathematica?] http://mathematica.stackexchange.com/questions/141581/can-one-create-a-custom-front-end-for-mathematica

I’d like to create my custom front-end for Mathematica. I know there’s a console interface (launched as math), which mostly works great, but it can’t really provide functionality of e.g. interactive ...

- asked by Ruslan (9 votes)

—————————-

[How to clear Integrate internal memory?] http://mathematica.stackexchange.com/questions/141324/how-to-clear-integrate-internal-memory

I noticed that when I call Integrate for the first time, on an integral that I know will take longer than the time limit I give it, it will abort for the first time, as expected when wrapped by ...

- asked by Nasser (9 votes), answered by J. M. (11 votes)

================================== Greatest hits from previous weeks: ==================================

[Creating legends for plots with multiple lines?] http://mathematica.stackexchange.com/questions/4025/creating-legends-for-plots-with-multiple-lines

So I have a graph with multiple lists, for e.g.

data = {{1,2}, {3,4}, {3,5}, {2,3} . . .}

If I then do ListLinePlot[Table[{#1,Log[b,#2]}&amp;@@@data, {b,1,10,2}]]
I have no way to generate a legend  ...

- asked by Eiyrioü von Kauyf (60 votes), answered by Jens (89 votes)

—————————-

[Labeling individual curves in Mathematica] http://mathematica.stackexchange.com/questions/4444/labeling-individual-curves-in-mathematica

I need to create a plot for export and inclusion in a report. Is there a better way to label curves than PlotLegends? From what I’ve read and my personal experience, PlotLegends is pretty bad.

Is ...

- asked by Tianxiang Xiong (49 votes), answered by Artes (39 votes)

================================== Can you answer these? ==================================

[GraphicsComplex dynamic colors] http://mathematica.stackexchange.com/questions/141489/graphicscomplex-dynamic-colors

I have a fairly large GraphicsComplex (surface mesh with more than several thousand vertices) and I want to visualize a scalar function that is defined on the vertices. I map the function to vertex ...

- asked by Beginner (6 votes)

—————————-

[how to efficiently generate all directed graphs with 6 vertices] http://mathematica.stackexchange.com/questions/141681/how-to-efficiently-generate-all-directed-graphs-with-6-vertices

I am attempting to generate all non-isomorphic directed graphs with 6 vertices using command ListGraphs[6, Directed].But it does not work efficiently and takes a month producing nothing.

Can anyone ...

- asked by Mike (6 votes)

—————————-

[Bug in Limit in version 11.1.0] http://mathematica.stackexchange.com/questions/141233/bug-in-limit-in-version-11-1-0

Bug introduced in version 11.1.0

The infinite limit

Assuming[a&gt;0&amp;&amp;b&gt;0,
  Limit[((1+a)*b*x)/Sqrt[1+(1+a)*b*x*((1+a)*b*x+Sqrt[1+(1+a)^2*b^2*x^2])],
    x-&gt;Infinity]]

gives the ...

- asked by Roman (5 votes)

25 Tuesday, March 28, 2017

==================================
Top new questions this week:
==================================

================================== Top new questions this week: ==================================

[Faster derangements?] http://mathematica.stackexchange.com/questions/140794/faster-derangements

I wonder what is the fastest method to generate derangements?

Both the Combinatorica function and Martin Ender’s answer to Permutations of lists of fixed even numbers are based on filtering the ...

- asked by Mr.Wizard (22 votes), answered by jkuczm (21 votes)

—————————-

[Why Except is so slow as compared to equivalent RegularExpression?] http://mathematica.stackexchange.com/questions/140752/why-except-is-so-slow-as-compared-to-equivalent-regularexpression

When comparing performance of the solutions suggested for this question I discovered that StringExpression involving Except is two orders of magnitude slower for large strings as compared to ...

- asked by Alexey Popkov (18 votes), answered by Alexey Popkov (20 votes)

—————————-

[FrameTicks setting for ”tick marks on all sides, but labels only on right and top”] http://mathematica.stackexchange.com/questions/140966/frameticks-setting-for-tick-marks-on-all-sides-but-labels-only-on-right-and-to

Short version: Is there a value for the FrameTicks option that retains the default tick marks on all sides, and puts tick labels only on the right and top sides?

I can imagine all manner of ...

- asked by kjo (15 votes), answered by Mr.Wizard (7 votes)

—————————-

[Quickly importing several thousands of jpg files?] http://mathematica.stackexchange.com/questions/140974/quickly-importing-several-thousands-of-jpg-files

I have several thousands of small .jpg files (30kb each) which I need to import into Mathematica. (I plan to use ImageDistance to investigate their differences.) I tried several ways to import these ...

- asked by Kagaratsch (14 votes), answered by Szabolcs (13 votes)

—————————-

[Select seems unusually slow] http://mathematica.stackexchange.com/questions/140861/select-seems-unusually-slow

I haven’t been doing nearly as much Mathematica as I really should for the past few months, and in order to get my head back in the game I’ve been using it to run roughshod over easy Project Euler ...

- asked by Pillsy (13 votes), answered by Bob Hanlon (10 votes)

—————————-

[Permutations of nested parentheses (Dyck words)] http://mathematica.stackexchange.com/questions/141127/permutations-of-nested-parentheses-dyck-words

How would I construct a function that outputs Dyck Words?

e.g. - there are 14 words in D8   :

`[[[[]]]], [[[][]]], [[[]][]], [[][[]]], [[[]]][], [[][][]], [][[[]]],
 [[][]][], [[]][[]],  ...

- asked by martin (11 votes), answered by Mr.Wizard (13 votes)

—————————-

[Bug: Library functions from older versions of Mathematica may crash in Mathematica 11.1 and conversely] http://mathematica.stackexchange.com/questions/140758/bug-library-functions-from-older-versions-of-mathematica-may-crash-in-mathemati

The following is a confirmed bug [CASE:3846875] that turned up in the prerelease 11.1.0 and is not solved in the official release.

This is a small example. Execute the following commands in ...

- asked by Fred Simons (11 votes)

================================== Greatest hits from previous weeks: ==================================

[How to make a Spherical Cow?] http://mathematica.stackexchange.com/questions/125043/how-to-make-a-spherical-cow

Being a theoretical physicist, I always have a great respect for Spherical Cow. So I thought about making one myself. I am not sure how can I create (something considered to be the simplest!) this ...

- asked by Sumit (60 votes), answered by andre (69 votes)

—————————-

[How to tell Mathematica that certain variables are real/imaginary, integer-valued, etc] http://mathematica.stackexchange.com/questions/66273/how-to-tell-mathematica-that-certain-variables-are-real-imaginary-integer-value

I’m trying to expedite some quantum mechanical calculations (expectation values etc.) by running them through Mathematica. When I say, for example,

u[x_] := Sqrt[2/L] * Sin[Pi * n * x / L]

and then ...

- asked by Matthew Brunetti (13 votes), answered by SquareOne (10 votes)

================================== Can you answer these? ==================================

[Why does LatticeReduce require integral or at least rational inputs?] http://mathematica.stackexchange.com/questions/141002/why-does-latticereduce-require-integral-or-at-least-rational-inputs

The function LatticeReduce in Mathematica implements the LLL algorithm. It requires the lattice basis to be described as integral or at least rational numbers.

Why so?

The LLL algorithm itself is ...

- asked by wdlang (3 votes)

—————————-

[Textual progress in console?] http://mathematica.stackexchange.com/questions/140675/textual-progress-in-console

Is there any way to get a textual progress bar (e.g. like the progressbar module in a python repl) when working in console mode?

Anything would be better than this:

- asked by user5601 (6 votes)

—————————-

[How to trigger an ”ErrorBox behavior”?] http://mathematica.stackexchange.com/questions/140979/how-to-trigger-an-errorbox-behavior

Here’s an example of what I mean by an ”ErrorBox behavior”. In the front end, if one evaluates the expression

Graphics[Circle[], ImageSize -&gt; Tiny, PlotRange -&gt; {All}]

(which includes the ...

- asked by kjo (7 votes)

26 Tuesday, March 21, 2017

==================================
Top new questions this week:
==================================

[V11.1: Effective methods to use paid functions economically] http://mathematica.stackexchange.com/questions/140261/v11-1-effective-methods-to-use-paid-functions-economically

In the newly released version 11.1, Mathematica introduces three new functions: WebSearch, WebImageSearch and TextTranslation that requires Service Credits. While I haven’t found much information ...

- asked by happy fish (30 votes), answered by Wjx (14 votes)

—————————-

[How do I disable the stack tracing feature in Mathematica 11?] http://mathematica.stackexchange.com/questions/140285/how-do-i-disable-the-stack-tracing-feature-in-mathematica-11

Bug was introduced in 11.0 and persisting through 11.1

It looks like the Mathematica 11 stack tracing feature (see red ellipsis in front of any warning message) prevents the garbage collector from ...

- asked by Shadowray (28 votes), answered by user6014 (23 votes)

—————————-

[Generative Adversarial Network] http://mathematica.stackexchange.com/questions/140294/generative-adversarial-network

Generative adversarial networks (GAN) is regarded as one of ”the most interesting idea in the last ten years in machine learning” by Yann LeCun. It can be used to generate photo-realistic images that ...

- asked by xslittlegrass (17 votes), answered by Taliesin Beynon (8 votes)

—————————-

[Modeling the spread of an infection in networked computers] http://mathematica.stackexchange.com/questions/140099/modeling-the-spread-of-an-infection-in-networked-computers

I would like to show the iterative stages of infection for problem 2 in this link.

In case the link dies, I have copied the text for the problem below:

One hundred computers are connected in a ...

- asked by martin (14 votes), answered by Martin Ender (24 votes)

—————————-

[how to remove the little × that shows up in frontend when typing?] http://mathematica.stackexchange.com/questions/140583/how-to-remove-the-little-x-that-shows-up-in-frontend-when-typing

Version 11.1 now shows a little grayed out x (a multiplication sign) when one is editing something, to warn them that the expression will be interpreted as the multiplication of what precedes and ...

- asked by Nasser (12 votes), answered by Nasser (18 votes)

—————————-

[Delete redundant x,y pairs] http://mathematica.stackexchange.com/questions/140571/delete-redundant-x-y-pairs

Working through the problems from Hazrat’s Mathematica book and there’s a simple exercise to find all the square numbers where n2 + m2 = h2   yields h  as an integer (I think they’re also called ...

- asked by Joe (10 votes), answered by kglr (13 votes)

—————————-

[Getting Compile to work with Visual Studio 2017 Community Edition] http://mathematica.stackexchange.com/questions/140071/getting-compile-to-work-with-visual-studio-2017-community-edition

The new Visual Studio is out since a week and I tried to get it to work with Mathematica (v 11.0). However the usual tricks for working with a new VS version fail here.

Related seems to be the ...

- asked by Sjoerd C. de Vries (10 votes)

================================== Greatest hits from previous weeks: ==================================

[1 Plot, 2 Scale/Axis] http://mathematica.stackexchange.com/questions/627/1-plot-2-scale-axis

I would like to plot those two datasets on top of each other. But they have very different range on the y  axis. How can I have two different axis?

I found the following on the help menu but quite ...

- asked by 500 (114 votes), answered by ArgentoSapiens (110 votes)

—————————-

[Assign the results from a Solve to variable(s)] http://mathematica.stackexchange.com/questions/6669/assign-the-results-from-a-solve-to-variables

I understand Mathematica can’t assign the results of a Solve to the unknowns because there may be more than 1 solution. How can I assign the 4 values of following result to variables?

- asked by stevenvh (34 votes), answered by Artes (25 votes)

================================== Can you answer these? ==================================

[Explaining error when using Part inside Module in Dataset] http://mathematica.stackexchange.com/questions/140541/explaining-error-when-using-part-inside-module-in-dataset

I have a vague recollection of seen an explanation for this, but I can not find it, so it may be a false memory. Will delete if duplicated.

Let ds be a simple Dataset

ds = Dataset@Table[
    ...

- asked by rhermans (4 votes)

—————————-

[Performance-driven approach to using Big Data without killing the hard-drive] http://mathematica.stackexchange.com/questions/140114/performance-driven-approach-to-using-big-data-without-killing-the-hard-drive

Situation

A calculation has to be done in which the amount of data is too much to fit into memory. Fortunately, only a part of the overall data set has to be known at a time. The preprocessing is ...

- asked by pbx (7 votes)

—————————-

[Bug with PlotLegends-¿Placed in GraphicsRow] http://mathematica.stackexchange.com/questions/140539/bug-with-plotlegends-placed-in-graphicsrow

Bug introduced in 11.0 and persisting through 11.1

The FrontEnd of Mathematica 11.1.0 on my Windows 7 box runs permanently at 100% CPU when I execute the following command:

...

- asked by RonH (3 votes)

27 Tuesday, March 14, 2017

==================================
Top new questions this week:
==================================

[How to implement a discrete data representation?] http://mathematica.stackexchange.com/questions/139818/how-to-implement-a-discrete-data-representation

I’m currently working with large datasets of ”discrete data”. Each of these is a multiset of real numbers of the form kS + B  , where k  is an integer, and S  (the ”scale”) and B  (the ”bias”) are ...

- asked by kjo (17 votes), answered by gwr (14 votes)

—————————-

[Mathematica incorrectly giving zero for partial derivative] http://mathematica.stackexchange.com/questions/139669/mathematica-incorrectly-giving-zero-for-partial-derivative

Bug introduced in 9.0.1 or earlier

Mathematica is incorrectly reporting that the partial derivative of a certain expression is zero.

I try to compute the following:

D[SymmetricPolynomial[3, {x1,  ...

- asked by Izaak Meckler (17 votes), answered by march (6 votes)

—————————-

[Finding vampire numbers] http://mathematica.stackexchange.com/questions/139808/finding-vampire-numbers

How to find vampire numbers by using Mathematica?

A number v = xy  with an even number n  of digits formed by multiplying a pair of n∕2  -digit numbers (where the digits are taken from the ...

- asked by vito (13 votes), answered by wolfies (8 votes)

—————————-

[Why do subsequent evaluations seem to be stopped by a False Condition (/;)?] http://mathematica.stackexchange.com/questions/139461/why-do-subsequent-evaluations-seem-to-be-stopped-by-a-false-condition

Exploring another problem and this example of @halirutan, I came across an evaluation behavior I don’t understand.

When g[] below is evaluated the first time, ig[] is evaluated and a message printed; ...

- asked by Michael E2 (12 votes), answered by Carl Woll (13 votes)

—————————-

[Bug? Numerical calculation error with FullSimplify and arbitrary precision] http://mathematica.stackexchange.com/questions/139697/bug-numerical-calculation-error-with-fullsimplify-and-arbitrary-precision

Bug introduced after 5.2, fixed in 8.0, reintroduced in 9.0 and persisting through 11.0.1

Is this a bug?

If I do

FullSimplify[n E^(0``10 n)]


then it returns

n/2

what is obviously incorrect.

...

- asked by David Bevan (10 votes)

—————————-

[Is there a convention on which name to use for a throwaway variable? (Like underscore in Python)] http://mathematica.stackexchange.com/questions/139622/is-there-a-convention-on-which-name-to-use-for-a-throwaway-variable-like-under

I would prefer to write {_, foo} = LongFunctionName[arg1, arg2] instead of
foo = LongFunctionName[arg1, arg2][[2]] or foo = Last @ LongFunctionName[arg1, arg2].
Using an actual name for the throwaway  ...

- asked by ZeitPolizei (10 votes), answered by Mr.Wizard (5 votes)

—————————-

[Extract images from large avi movies (50-100 GB)] http://mathematica.stackexchange.com/questions/139819/extract-images-from-large-avi-movies-50-100-gb

I will get large RGB avi files (35 Hz, 1600*1200 pixels) of up to 100 GB size. All three channels contain the same grayscale image.

I want to extract each avi file into one channel png images.

To do ...

- asked by mrz (8 votes), answered by mrz (11 votes)

================================== Greatest hits from previous weeks: ==================================

[How to tell Mathematica that certain variables are real/imaginary, integer-valued, etc] http://mathematica.stackexchange.com/questions/66273/how-to-tell-mathematica-that-certain-variables-are-real-imaginary-integer-value

I’m trying to expedite some quantum mechanical calculations by running them through Mathematica. Expectation values and stuff like that. When I say, for example,

u[x_] := Sqrt[2/L] * Sin[Pi * n * x /  ...

- asked by Matthew Brunetti (11 votes), answered by SquareOne (9 votes)

—————————-

[Where can I find examples of good Mathematica programming practice?] http://mathematica.stackexchange.com/questions/18/where-can-i-find-examples-of-good-mathematica-programming-practice

I consider myself a pretty good Mathematica programmer, but I’m always looking out for ways to either improve my way of doing things in Mathematica, or to see if there’s something nifty that I haven’t ...

- asked by J. M. (460 votes), answered by faysou (404 votes)

================================== Can you answer these? ==================================

[Integrating rational functions of several variables over ℍ4   ] http://mathematica.stackexchange.com/questions/139631/integrating-rational-functions-of-several-variables-over-mathbbh4

Let W  be a rational function of 8  variables a,b,c,d,e,f,g,h  from this file, e.g.:

W = (256*b*d*f*(a^5 + b^4*(c - 2*e) - a^4*(3*c + 2*e) - c*(c^2 + d^2)*(e^2 + f^2) + a^3*(2*b^2 + 3*c^2 + d^2 +  ...

- asked by Ricardo Buring (4 votes)

—————————-

[Best Wolfram tool for interactive web-based calculator] http://mathematica.stackexchange.com/questions/139954/best-wolfram-tool-for-interactive-web-based-calculator

A colleague is considering re-implementing this online ”Photon Propulsion Calculator” using a Mathematica-based product. I wanted to ask the community which product would be best.

WebMathematica

...

- asked by ConvexMartian (8 votes)

—————————-

[How to get rid of a built-in context from autocomplete?] http://mathematica.stackexchange.com/questions/139783/how-to-get-rid-of-a-built-in-context-from-autocomplete

I have noticed that when I type the name of built-in function Limit in Mathematica, the autocomplete suggests two variants at the top: the first one is the working one, and the second one is just ...

- asked by user372003 (4 votes)

28 Tuesday, March 7, 2017

==================================
Top new questions this week:
==================================

[What are some common issues with fitting functions to data?] http://mathematica.stackexchange.com/questions/139038/what-are-some-common-issues-with-fitting-functions-to-data

Mathematica has numerous functions designed to, or capable of, fitting known functions, and finding unknown functions to match data sets. What are some common issues that come with finding those fits? ...

- asked by Feyre (20 votes), answered by Feyre (21 votes)

—————————-

[Notebook’s TaggingRules inherit too much] http://mathematica.stackexchange.com/questions/139017/notebooks-taggingrules-inherit-too-much

Bug introduced in V10.4 or earlier and persisting through 11.0.1

[CASE:3852725] was created

[...] I have forwarded an incident report to our developers with the information you provided. ...

- asked by Kuba (14 votes), answered by Kuba (3 votes)

—————————-

[Is ExportString defective in V11?] http://mathematica.stackexchange.com/questions/138932/is-exportstring-defective-in-v11

Mathematica doesn’t do the best job of exporting figures with shading or transparency to vector graphics formats such as PDF.

A common trick employed here and elsewhere on the web to workaround this ...

- asked by Quantum_Oli (11 votes)

—————————-

[Commands to stop and continue evaluation without Debugger] http://mathematica.stackexchange.com/questions/139377/commands-to-stop-and-continue-evaluation-without-debugger

I would like to stop the evaluation somehwere at a specifiy line in a notebook. Then I could for example check the state of some variables.

After that I would like to continue the evaluation from the ...

- asked by lio (10 votes), answered by Szabolcs (9 votes)

—————————-

[How am I misusing EvenQ, or, how are EvenQ and (Mod[2,#]==0)& differently evaluated?] http://mathematica.stackexchange.com/questions/139281/how-am-i-misusing-evenq-or-how-are-evenq-and-mod2-0-differently-evalua

While working on a problem, I was using EvenQ in a RegionPlot. I came across this interesting case (simplified here for specificity). I expected to see a bunch of stripes, but got nothing:

...

- asked by Piquan (10 votes), answered by Mr.Wizard (9 votes)

—————————-

[Partition a list by count of a number] http://mathematica.stackexchange.com/questions/138905/partition-a-list-by-count-of-a-number

I want to take this list when the 2 appear 3 times

SeedRandom[1]
list = RandomChoice[{.2, .5, .3} -&gt; {1, 2, 3}, 20]

{3,1,3,1,2,1,2,2,2,3,2,3,2,2,3,3,3,2,2,2}



Hope to get {{3, 1, 3, 1, 2, 1,  ...

- asked by yode (10 votes), answered by Mr.Wizard (5 votes)

—————————-

[Why SciDraw can not handle the StreamPlot?] http://mathematica.stackexchange.com/questions/138926/why-scidraw-can-not-handle-the-streamplot

I find that the package SciDraw is suitable for preparing the figure in the thesis. When I use it to plot the line, it works well. For example

<<SciDraw`
 ...

- asked by Ice0cean (10 votes), answered by Szabolcs (11 votes)

================================== Greatest hits from previous weeks: ==================================

[How to express trigonometric equation in terms of of given trigonometric function?] http://mathematica.stackexchange.com/questions/434/how-to-express-trigonometric-equation-in-terms-of-of-given-trigonometric-functio

How can I express a trigonometric equation / identity in terms of a given trigonometric function?

using following trigonometric identities

Sin[x]^2+Cos[x]^2==1
Sin[x]/Cos[x]==Tan[x]
 ...

- asked by Prashant Bhate (25 votes), answered by Simon (32 votes)

—————————-

[Calculate the 2D Fourier transform of an Image] http://mathematica.stackexchange.com/questions/29203/calculate-the-2d-fourier-transform-of-an-image

I am new to Mathematica, and using version 8.0.

I would like to calculate the 2D Fourier Transform of an Image with Mathematica and plot the magnitude and phase spectrum, as well as reconstruct the ...

- asked by user8727 (5 votes), answered by Nasser (27 votes)

================================== Can you answer these? ==================================

[Two-Point correlation function of Ising data is not giving expected results] http://mathematica.stackexchange.com/questions/139016/two-point-correlation-function-of-ising-data-is-not-giving-expected-results

Due to the nature of my problem, and readers perhaps not having a physics background, I need to give some context to my problem which is intrinsic to it. The problem however is not a physics one, but ...

- asked by Luca Pontiggia (3 votes)

—————————-

[Evaluating an expectation expressed by a difficult expression] http://mathematica.stackexchange.com/questions/138917/evaluating-an-expectation-expressed-by-a-difficult-expression

Background

I have a 2-dimensional space. The receiver is at the center. The locations of transmitters are given by the PPP Φ  with density λ  . The serving transmitter is the one that is ...

- asked by George Harnandez (3 votes)

—————————-

[How to control indentation of a cell relative to it’s parent?] http://mathematica.stackexchange.com/questions/138971/how-to-control-indentation-of-a-cell-relative-to-its-parent

Is there a stylesheet property that can be set to control the extra level of indentation of a cell in its group (I don’t want to specify absolute CellMargins)?

Carl suggests in the comments to use ...

- asked by user5601 (3 votes)

29 Tuesday, February 28, 2017

==================================
Top new questions this week:
==================================

[Parallelize Map and ParallelMap] http://mathematica.stackexchange.com/questions/138476/parallelize-map-and-parallelmap

Bug introduced in 8.0 and persisting through 11.0.1 or later

It is stated in the documentation that

  Parallelize[Map[f, expr]] is equivalent to ParallelMap[f, expr].

But what about these ...

- asked by Mher (29 votes), answered by Szabolcs (23 votes)

—————————-

[Can we intelligently control evaluation in Thread?] http://mathematica.stackexchange.com/questions/138661/can-we-intelligently-control-evaluation-in-thread

This is a bid at creating a canonical Q&A.

Many questions have been asked that come down to the fact that Thread evaluates its first argument before threading is attempted. In a few minutes I ...

- asked by Mr.Wizard (27 votes), answered by Mr.Wizard (21 votes)

—————————-

[Learn Mathematica (Wolfram) Language in one day] http://mathematica.stackexchange.com/questions/138366/learn-mathematica-wolfram-language-in-one-day

Currently I am trying to learn Python. Searching for relevant material I came across

X in Y minutes

and books with titles such as Learn Python in one day, in 24 hours, etc.

Similar material exists ...

- asked by dimitris (23 votes), answered by masterxilo (5 votes)

—————————-

[Puzzle — 20 People to consume 20 units of food under constraints] http://mathematica.stackexchange.com/questions/138637/puzzle-20-people-to-consume-20-units-of-food-under-constraints

I am learning Mathematica because I love it. I also love solving puzzles so I think it would be a nice way to learn Mathematica through puzzles. This is first puzzle in series I intend to solve.

So ...

- asked by Jawad_Mansoor (14 votes), answered by Mr.Wizard (18 votes)

—————————-

[Compute the curvature of a bent stack of paper] http://mathematica.stackexchange.com/questions/138583/compute-the-curvature-of-a-bent-stack-of-paper

My goal is to link the curvature of a bent stack of paper in a wind tunnel to its bending modulus B  , knowing all the other physical properties. To this end, I would like to reproduce the numerical ...

- asked by yketa (12 votes), answered by xzczd (8 votes)

—————————-

[WordOrientation does not work in v11?] http://mathematica.stackexchange.com/questions/138811/wordorientation-does-not-work-in-v11

Bug introduced in 11.0.1

It seems that WordOrientation does not work in v11. The sample code

input = ExampleData[{"Text", "AliceInWonderland"}];
WordCloud[input, WordOrientation -&gt; "Random"]

...

- asked by Lem.ma (11 votes)

—————————-

[Code request: Make ”copy formatted code” bulletproof] http://mathematica.stackexchange.com/questions/138436/code-request-make-copy-formatted-code-bulletproof

With the GeneralUtilities‘PrintDefinitions functions comes a usable code formatting engine. On this site, most of the time we share code. I believe it would be awesome to have a robust button that ...

- asked by halirutan (10 votes)

================================== Greatest hits from previous weeks: ==================================

[Why round to even integers?] http://mathematica.stackexchange.com/questions/2116/why-round-to-even-integers

According to the Mathematica help:

Round rounds numbers of the form x.5 toward the nearest even integer.

For example:

Round[{0.5, 1.5, 2.5, 3.5, 4.5}]


gives

{0, 2, 2, 4, 4}

What’s the ...

- asked by wxffles (61 votes), answered by Per Alexandersson (37 votes)

—————————-

[Assign the results from a Solve to variable(s)] http://mathematica.stackexchange.com/questions/6669/assign-the-results-from-a-solve-to-variables

I understand Mathematica can’t assign the results of a Solve to the unknowns because there may be more than 1 solution. How can I assign the 4 values of following result to variables?

- asked by stevenvh (33 votes), answered by Artes (24 votes)

================================== Can you answer these? ==================================

[Plotting a 2D slice of a 3D function] http://mathematica.stackexchange.com/questions/138808/plotting-a-2d-slice-of-a-3d-function

Id like to plot (Sqrt[x] + Sqrt[y] + Sqrt[z])^2 in a slice defined by x+y+z=1

I figured out similar problem 5 years ago, but it was a bit involved, ie, needing 10 lines of Mathematica code. Is there ...

- asked by Yaroslav Bulatov (2 votes)

—————————-

[Export of Plot3D function completely different from the render within Mathematica] http://mathematica.stackexchange.com/questions/138412/export-of-plot3d-function-completely-different-from-the-render-within-mathematic

I am plotting a simple function:

Plot3D[-RandomReal[{0, 10}] Cos[x/3] Cos[y/3],
  {x, -π, π}, {y, -π, π},
  Axes -&gt; False,
  Boxed -&gt; False,
  BoundaryStyle -&gt; None,
  Mesh -&gt; None]

...

- asked by waffl (1 vote)

—————————-

[CreateExecutable returns $Failed] http://mathematica.stackexchange.com/questions/138328/createexecutable-returns-failed

My platform is win10 64b, Mathematica 11 and Visual Studio 2015. When I apply CreateExecutable, it always returns $Failed. The configuration is right. Please what is the problem? Thank you.

...

- asked by tu312 (1 vote)

30 Tuesday, February 21, 2017

==================================
Top new questions this week:
==================================

[How can I adaptively simplify a curved shape?] http://mathematica.stackexchange.com/questions/137937/how-can-i-adaptively-simplify-a-curved-shape

For the purposes of creating a publication-quality plot marker I wish to convert a font glyph into a simplified Polygon where points are taken adaptively according to curvature of the boundary. ...

- asked by Alexey Popkov (22 votes), answered by Szabolcs (29 votes)

—————————-

[Can Mathematica be used to make anamorphic distortions like these?] http://mathematica.stackexchange.com/questions/137853/can-mathematica-be-used-to-make-anamorphic-distortions-like-these

We have all see these sidewalk and street images that appear to be 3D based on the viewers perspective, but then wildly distort when viewed from a different perspective.

Seems to me anamorphic ...

- asked by R Hall (12 votes), answered by Simon Woods (10 votes)

—————————-

[How to implement lane-change rules for Nagel Schreckenberg model] http://mathematica.stackexchange.com/questions/138138/how-to-implement-lane-change-rules-for-nagel-schreckenberg-model

I am trying to extend the Nagel-Schreckenberg model for traffic flow to include two lanes of traffic.

I have a function that generates information about a random initial road configuration. A road ...

- asked by jlrawden (11 votes), answered by Ali Hashmi (5 votes)

—————————-

[How to make a custom NN layer in Mathematica?] http://mathematica.stackexchange.com/questions/138230/how-to-make-a-custom-nn-layer-in-mathematica

Is there a way to create our own custom layers for Neural Networks in Mathematica ? I suspect it should be possible, any pointers or directions on how to go about it?

I am interested in ...

- asked by Andy Stow Away (9 votes)

—————————-

[How to build private function with built-in function’s option] http://mathematica.stackexchange.com/questions/138126/how-to-build-private-function-with-built-in-functions-option

Since this code work well:

Needs["GeneralUtilities`"]
GeneralUtilities`BenchmarkPlot[{SortBy[#, Identity] &amp;, Sort}, Range,
 "IncludeFits" -&gt; True, TimeConstraint -&gt; 8]

I want to set ...

- asked by yode (9 votes), answered by Mr.Wizard (11 votes)

—————————-

[Doing combinations of sub-sublists] http://mathematica.stackexchange.com/questions/138178/doing-combinations-of-sub-sublists

To create a list of all the possible combinations of a sublist. I have a list, somewhat resembling the following format:

{{{a1, a2}, {b1}}, {{a1, a2}, {c1, c2}}, {{a1, a2}, {c1, c2}, {d1, d2}}}

...

- asked by Andrew Johnson (8 votes), answered by halirutan (11 votes)

—————————-

[Warning: FrontEnd crash with ‘Graphics@InfiniteLine‘ for unknown symbolic coordinates] http://mathematica.stackexchange.com/questions/137847/warning-frontend-crash-with-graphicsinfiniteline-for-unknown-symbolic-coordi

Bug introduced in 10.0 and persisting through 11.0.1 InfiniteLine is new in 10.0.

  [CASE:3840702] From your description, I gather you are noticing an unexpected crash
  while trying to evaluate  ...

- asked by masterxilo (8 votes)

================================== Greatest hits from previous weeks: ==================================

[How to add a vertical line to a plot] http://mathematica.stackexchange.com/questions/3561/how-to-add-a-vertical-line-to-a-plot

In the plot below I would like to add two vertical lines at x = π15 ± 210   . How can I do that?

f[x_] := (x^2 z)/((x^2 - y^2)^2 + 4 q^2 x^2) /. {y -&gt; π/15, z -&gt; 1, q -&gt;  ...

- asked by sjdh (33 votes), answered by Ajasja (49 votes)

—————————-

[Can Mathematica do symbolic linear algebra?] http://mathematica.stackexchange.com/questions/3242/can-mathematica-do-symbolic-linear-algebra

For instance, is there some way I can say ”let A and B be arbitrary real m  × n  and k × m  matrices,

Simplify[Transpose[Transpose[A].Transpose[B]]]" and Mathematica would simplify it to B.A?
 ...

- asked by nikie (42 votes), answered by helen (21 votes)

================================== Can you answer these? ==================================

[Calculate PDF of difference of Max and Min for Gaussian random variables] http://mathematica.stackexchange.com/questions/138027/calculate-pdf-of-difference-of-max-and-min-for-gaussian-random-variables

Although this should be a standard question I didn’t find it in SE, and it was a nice exercise in Mathematica.

Let x  and y  be two independent Gaussian random variables with distribution N (0,1)  . ...

- asked by Dr. Wolfgang Hintze (3 votes)

—————————-

[Implementing t-SNE (t-Distributed Stochastic Neighbor Embedding)] http://mathematica.stackexchange.com/questions/137955/implementing-t-sne-t-distributed-stochastic-neighbor-embedding

Context

Six months ago @M.R. asked about an implementation of the
t-Distributed Stochastic Neighbor Embedding (t-SNE) algorithm by van der
Maaten and Hinton (2008). (@M.R.s question)

@Alexey  ...

- asked by SumNeuron (3 votes)

—————————-

[Is there an easy way to to collect a large number variables into a list or list of lists?] http://mathematica.stackexchange.com/questions/138225/is-there-an-easy-way-to-to-collect-a-large-number-variables-into-a-list-or-list

I have a large number of variables in a notebook from a data analysis routine, the results of which now need to be fed through a mathematical model and various items for visualization.

For example, ...

- asked by Joe Kissling (2 votes)

31 Tuesday, February 14, 2017

==================================
Top new questions this week:
==================================

[How to generate a mesh with quadrilateral elements?] http://mathematica.stackexchange.com/questions/137479/how-to-generate-a-mesh-with-quadrilateral-elements

I have the following code that generates a finite element mesh:


Needs["NDSolve`FEM`"]
order = 2;
mesh = ToElementMesh[
DiscretizeGraphics[
GraphicsComplex[{{0, 4}, {5, 4}, {5, 0}, {8, 0}, {8,  ...

- asked by Diogo (13 votes), answered by Young (12 votes)

—————————-

[Why can’t I plot Log[Gamma[x]] for x ¿ 170?] http://mathematica.stackexchange.com/questions/137666/why-cant-i-plot-loggammax-for-x-170

Bug introduced in 11.0

For some reason I can’t plot Log[Gamma[x]] for values of x larger than approximately 170:

Plot[Log[Gamma[x]], {x, 130, 200}, PlotRange -&gt; All]

It works perfectly well ...

- asked by Felix (11 votes), answered by Szabolcs (12 votes)

—————————-

[Finding the number of odd quintinomial coefficients] http://mathematica.stackexchange.com/questions/137692/finding-the-number-of-odd-quintinomial-coefficients

I am searching for the number of odd coefficients of

(x4 + x3 + x2 + x + 1)n

for arbitrary n  .

It took some hours to compute the result for n = 12207  . There are 16333  odd ...

- asked by Jenny_mathy (10 votes), answered by Carl Woll (15 votes)

—————————-

[Possible bug with RegionPlot] http://mathematica.stackexchange.com/questions/137273/possible-bug-with-regionplot

RegionPlot[ImplicitRegion[(2 x - 1)/(x - 1) &lt; 3/2, {x, y}],
 PlotRange -&gt; {{-9, 9}, {-9, 9}}]

Just checking whether anyone else can replicate this. Can anybody confirm such behavior and, ...

- asked by mathe (10 votes), answered by Jason B. (8 votes)

—————————-

[List processing] http://mathematica.stackexchange.com/questions/137306/list-processing

Suppose I have a list that looks like the following (Town names and total distance to that town)

resupply = {
  {"Coleman", 0},
  {"Highwood House", 106},
  {"Canmore", 229},
  {"Exshaw", 245},
   ...

- asked by Tom De Vries (9 votes), answered by Kuba (19 votes)

—————————-

[How to superimpose plots and graphics in the same coordinate system?] http://mathematica.stackexchange.com/questions/137408/how-to-superimpose-plots-and-graphics-in-the-same-coordinate-system

NB: I am aware that ”plots” are graphics too, so the title would be more precisely worded if ”graphics” were replaced by ”non-plot graphics”.

EDIT: I have edited my original example to make the ...

- asked by kjo (8 votes), answered by Bob Hanlon (5 votes)

—————————-

[Unit tests for Graphics or FE boxes] http://mathematica.stackexchange.com/questions/137541/unit-tests-for-graphics-or-fe-boxes

Consider the following expression with bad syntax:

Graphics[foo]

How can I detect the error and retrieve the error message programmatically, so I can check for it in unit tests?

- asked by Szabolcs (7 votes), answered by rcollyer (9 votes)

================================== Greatest hits from previous weeks: ==================================

[Labeling individual curves in Mathematica] http://mathematica.stackexchange.com/questions/4444/labeling-individual-curves-in-mathematica

I need to create a plot for export and inclusion in a report. Is there a better way to label curves than PlotLegends? From what I’ve read and my personal experience, PlotLegends is pretty bad.

Is ...

- asked by Tianxiang Xiong (47 votes), answered by Artes (38 votes)

—————————-

[Why this real integral yields imaginary results?] http://mathematica.stackexchange.com/questions/127301/why-this-real-integral-yields-imaginary-results

Integrate[(y - y^2 + x - x^2 + 2*x*y)/(1 - x - y),{x,0,1},{y, 0, 1}]

The above integral yields -1-4Iπ/3 in Mathematica. Since the integrand is real (although divergent at some points), how does ...

- asked by Chong Wang (16 votes), answered by bbgodfrey (19 votes)

================================== Can you answer these? ==================================

[How to convert ‘LogTicks[0, 2][[1, 2]]‘ to a regular number] http://mathematica.stackexchange.com/questions/137208/how-to-convert-logticks0-21-2-to-a-regular-number

I want to convert the 10i  tick labels generated by LogTicks of the CustomTicks package to regular numbers. The first tick label is in element [[1,2]] of the object generated by LogTicks. FullForm ...

- asked by Felix (1 vote)

—————————-

[Solving the Euler-Lagrange equation with NDSolve‘ProcessEquations] http://mathematica.stackexchange.com/questions/137292/solving-the-euler-lagrange-equation-with-ndsolveprocessequations

I would like to compute the shortest distance between a number on pairs of points on a 2-dimensional Riemanniann statistical manifold (Negative Binomial distributions manifold, equipped with the Rao’s ...

- asked by C. Manté (1 vote)

—————————-

[Constraining the independent variable in a control system] http://mathematica.stackexchange.com/questions/137581/constraining-the-independent-variable-in-a-control-system

For an analog closed loop feedback control, I can do the following to model the response of a second-order physical system with an order 1 zeros polynomial to a step disturbance. I have a proportional ...

- asked by David Ollodart (2 votes)

32 Tuesday, February 7, 2017

==================================
Top new questions this week:
==================================

[Code that generates a mandala] http://mathematica.stackexchange.com/questions/136974/code-that-generates-a-mandala

My little brother asked me to print original mandalas for coloring. I would like some idea on how to create them, but without color, so he can color them.

examples

- asked by zeros (31 votes), answered by Anton Antonov (48 votes)

—————————-

[How to make Mathematica variables declarative instead of just-in-time?] http://mathematica.stackexchange.com/questions/136833/how-to-make-mathematica-variables-declarative-instead-of-just-in-time

Is there a way to have Mathematica at the notebook level
(SetOptions[EvaluationNotebook[], CellContext -&gt; Notebook])
only uses a set of declared variables in the notebook context. Any variables  ...

- asked by Edmund (27 votes), answered by rcollyer (25 votes)

—————————-

[Shorthand for map at level 2] http://mathematica.stackexchange.com/questions/136751/shorthand-for-map-at-level-2

I love the shorthand /@. It is amazing for readability (and laziness when typing).
However, right now I find that I need Map at level 2, i.e.
Map[f, List[List[a,b],List[c,d]], {2}], a lot and Id wish  ...

- asked by Kvothe (16 votes), answered by Mr.Wizard (19 votes)

—————————-

[Proteins, ProteinData, WolframAlpha] http://mathematica.stackexchange.com/questions/136741/proteins-proteindata-wolframalpha

Apologies in advance, this is the first I’ve messed with ProteinData and access through WolframAlpha, so clearly I may not know how Mathematica and Alpha decide on what is the ’right way’ to ask ...

- asked by flip (15 votes), answered by J. M. (10 votes)

—————————-

[Simplifying a reverse Fold for a Query] http://mathematica.stackexchange.com/questions/136856/simplifying-a-reverse-fold-for-a-query

Is there a simpler way to parametrize this tail-recursive expression to be applied as a Query (for processing a nested Association)? The pattern is shown by example with first 3 levels:

- asked by alancalvitti (11 votes), answered by Edmund (10 votes)

—————————-

[Where is Abbott? How to make logograms from the film ”Arrival”?] http://mathematica.stackexchange.com/questions/137156/where-is-abbott-how-to-make-logograms-from-the-film-arrival

The film Arrival showed Wolfram Language code in action analysing alien logograms. A recent blog describes some details and mentions a live-coding video by Christopher Wolfam. See also Stephen ...

- asked by KennyColnago (8 votes), answered by KennyColnago (10 votes)

—————————-

[How to implement neural style transfer?] http://mathematica.stackexchange.com/questions/136704/how-to-implement-neural-style-transfer

In the paper A Neural Algorithm of Artistic Style, Leon A. Gatys et all. describe a process of extracting the content and style vectors from an image separately. They use this technique to generate ...

- asked by M.R. (8 votes)

================================== Greatest hits from previous weeks: ==================================

[How to add a vertical line to a plot] http://mathematica.stackexchange.com/questions/3561/how-to-add-a-vertical-line-to-a-plot

In the plot below I would like to add two vertical lines at x = π15 ± 210   . How can I do that?

f[x_] := (x^2 z)/((x^2 - y^2)^2 + 4 q^2 x^2) /. {y -&gt; π/15, z -&gt; 1, q -&gt;  ...

- asked by sjdh (32 votes), answered by Ajasja (48 votes)

—————————-

[Calculate the 2D Fourier transform of an Image] http://mathematica.stackexchange.com/questions/29203/calculate-the-2d-fourier-transform-of-an-image

I am new to Mathematica, and using version 8.0.

I would like to calculate the 2D Fourier Transform of an Image with Mathematica and plot the magnitude and phase spectrum, as well as reconstruct the ...

- asked by user8727 (5 votes), answered by Nasser (27 votes)

================================== Can you answer these? ==================================

[Nonsparse sparse array crashes kernel on windows] http://mathematica.stackexchange.com/questions/136835/nonsparse-sparse-array-crashes-kernel-on-windows

On win 10, 64 bit, version 11.0.1, my kernel just started crashing for no reason as for as I can see. Does/should the following crash your kernel?

sparse = SparseArray[ArrayRules[RandomInteger[{1,  ...

- asked by Coolwater (6 votes)

—————————-

[How to visualize the vorticity of a 3D velocity field?] http://mathematica.stackexchange.com/questions/136917/how-to-visualize-the-vorticity-of-a-3d-velocity-field

I have a snapshot of a system with 50 particles.

The snapshot is a list of 3 coordinates and 3 velocities per each particle. Namely, (x,y,z, ˙x, ˙y, ˙z)  , which AKA phase space ...

- asked by 0x90 (5 votes)

—————————-

[Finding line segments on the image by using ImageLines] http://mathematica.stackexchange.com/questions/136795/finding-line-segments-on-the-image-by-using-imagelines

There is an image from wolfram documentation

I want to find and highlight lines on the following image

I tried:

img = Import["http://imgur.com/NbNwYWC.png"]

lines = ImageLines[EdgeDetect[img],  ...

- asked by vito (3 votes)

33 Tuesday, January 31, 2017

==================================
Top new questions this week:
==================================

[How to get a specified number of points that are nearly equally spaced in a closed rectangle] http://mathematica.stackexchange.com/questions/136447/how-to-get-a-specified-number-of-points-that-are-nearly-equally-spaced-in-a-clos

TriangulateMesh is almost the right tool for this problem. For example,

numb = 113;
region = BoundaryMeshRegion[{{0, 0}, {3, 0}, {3, 1}, {0, 1}}, Line[{1, 2, 3, 4, 1}]];
mesh =  ...

- asked by Ted Ersek (17 votes), answered by Szabolcs (15 votes)

—————————-

[Tutorial on creating publication quality documents in Mathematica?] http://mathematica.stackexchange.com/questions/136426/tutorial-on-creating-publication-quality-documents-in-mathematica

Are there books or tutorials that walk one through creating a professional publication quality notebook?

For example, I would like to create a two column article using an IEEE format. Is this ...

- asked by Doug Kimzey (13 votes)

—————————-

[Type conversions] http://mathematica.stackexchange.com/questions/136476/type-conversions

I have the following list, each element of which is of type string:

”abc”, ”def”,”2”,”ghi”,”7”

Is there an efficient way to arrive at:

”abcdef”, 2,”ghi”,7

where adjacent alphabetic elements ...

- asked by Suite401 (12 votes), answered by Bob Hanlon (8 votes)

—————————-

[Alternatives and the Flat attribute] http://mathematica.stackexchange.com/questions/136157/alternatives-and-the-flat-attribute

When a head has the attribute Flat then the pattern matcher is able to pick out a sublist of its arguments, even though the structure doesn’t match:

SetAttributes[f, Flat];
f[a, b, c, d] /. f[a, b]  ...

- asked by Martin Ender (11 votes)

—————————-

[Assign names to Dataset columns] http://mathematica.stackexchange.com/questions/136422/assign-names-to-dataset-columns

I am constructing a dataset like so:

data = Dataset[AssociationThread[Keys[characterCounts], charFrequencies]]

which gives me a dataset that looks like this:

This is all fine, but as you can ...

- asked by damjandd (10 votes), answered by Kuba (10 votes)

—————————-

[Dataset interferes with SeedRandom] http://mathematica.stackexchange.com/questions/136339/dataset-interferes-with-seedrandom

This seems like a pretty awful bug:

SeedRandom[1];
RandomInteger[10, 10]

Out: {1,4,0,7,0,0,8,6,0,4}


While:

SeedRandom[1];
Dataset[&lt;|a -&gt; 1, b -&gt; 2|&gt;];
RandomInteger[10, 10]

Out:  ...

- asked by Mohammed AlQuraishi (10 votes)

—————————-

[Problem with integrating DiracDelta] http://mathematica.stackexchange.com/questions/136214/problem-with-integrating-diracdelta

I thought I had found a bug in Mathematica and reported it already in version 9, since it wasn’t fixed in version 10 or 11 I reported it two more times but I never get any reply whatsoever so I’m ...

- asked by user3777022 (10 votes), answered by Julien Kluge (8 votes)

================================== Greatest hits from previous weeks: ==================================

[Assign the results from a Solve to variable(s)] http://mathematica.stackexchange.com/questions/6669/assign-the-results-from-a-solve-to-variables

I understand Mathematica can’t assign the results of a Solve to the unknowns because there may be more than 1 solution. How can I assign the 4 values of following result to variables?

- asked by stevenvh (30 votes), answered by Artes (22 votes)

—————————-

[How to create a fascinating QR code like this?] http://mathematica.stackexchange.com/questions/120041/how-to-create-a-fascinating-qr-code-like-this

Check the facinating QRCode in my profile page here

You can find that this QRCode is some sort of intriguing as the QRCode is a IMAGE ITSELF!!!

So my question is, how to create such a QRCode ...

- asked by Wjx (24 votes), answered by Wjx (19 votes)

================================== Can you answer these? ==================================

[How to Approximate at Non-differentiable Point (forced Series Expansion around Branch Cut)] http://mathematica.stackexchange.com/questions/136395/how-to-approximate-at-non-differentiable-point-forced-series-expansion-around-b

I need a numerical approximation around some functions at x = 0− from the left side, where x = 0  is unfortunately the right end of the domain (in the reals) so the functions are not ...

- asked by Lee David Chung Lin (3 votes)

—————————-

[3D reconstruction of a 2D SEM image] http://mathematica.stackexchange.com/questions/136284/3d-reconstruction-of-a-2d-sem-image

I am curious if Mathematica could do reconstruction of a 2D SEM image into a 3D. It is the same what can be done by MountainsMap SEM software http://www.digitalsurf.fr/en/mntsem.html

Visually it ...

- asked by Viacheslav Plotnikov (4 votes)

—————————-

[Help needed in Understand the following program in solving a stiff nonlinear differential equation] http://mathematica.stackexchange.com/questions/136607/help-needed-in-understand-the-following-program-in-solving-a-stiff-nonlinear-dif

I am trying to solve a particular Cauchy problem given by

I found from a particular paper that the solutions looks like

For the auxiliary conditions

For only specific values of ai

I ...

- asked by kernel_panic (1 vote)

34 Tuesday, January 24, 2017

==================================
Top new questions this week:
==================================

[My Girlfriend is going to prison...Save her with Math] http://mathematica.stackexchange.com/questions/135937/my-girlfriend-is-going-to-prison-save-her-with-math

Salacious title, but true story.

 dmethyl1 = {
      {0, 0},
      {.25, 1},
      {.5, 7},
      {1, 26},
      {1.5, 40},
      {2, 45},
      {2.5, 45},
      {3, 44},
      {3.5, 44},
      {4,  ...

- asked by Prisoners Dilema (35 votes), answered by bobthechemist (22 votes)

—————————-

[How to use the iterator in Mathematica] http://mathematica.stackexchange.com/questions/135916/how-to-use-the-iterator-in-mathematica

I find the Mathematica has the iterator data structure. We can build some iterators like this:

Constant iterator

GeneralUtilities`ConstantIterator[5]

Key value iterator

...

- asked by yode (15 votes), answered by Michael E2 (15 votes)

—————————-

[SquaresR memory leak?] http://mathematica.stackexchange.com/questions/135781/squaresr-memory-leak

I have tried the following code in Mathematica 11.0.1.0 on my MacBook:

$HistoryLength = 0;
ClearAll["Global`*"];
ClearSystemCache[];
MemoryInUse[]

AbsoluteTiming[Do[SquaresR[2, i], {i, 1000000}];]

...

- asked by outofmemory (12 votes), answered by Mr.Wizard (18 votes)

—————————-

[SetOptions locally?] http://mathematica.stackexchange.com/questions/136005/setoptions-locally

Is there a way to SetOptions locally? For example, I have a Module and inside it I am doing a lot of Plots with similar options. If I do a SetOptions[Plot, ...] inside the Module, the change ...

- asked by becko (11 votes), answered by J. M. (12 votes)

—————————-

[Understanding simple numerical calculation] http://mathematica.stackexchange.com/questions/135636/understanding-simple-numerical-calculation

I am trying to understand why N[0.1]//FullForm returns 0.1’ (A). Indeed, 0.1  in base two is 0.000110011001100110011...  . If I truncate this number to the first 52 digits and convert it back to base ...

- asked by anderstood (11 votes), answered by Michael E2 (18 votes)

—————————-

[How to work with Date calculations?] http://mathematica.stackexchange.com/questions/135713/how-to-work-with-date-calculations

I have never worked using the DateObject function

But I suspect there must be a (easy) way of doing it.

I want to find out, when in the future, from which point, that the cumulative days of not ...

- asked by Chen Stats Yu (10 votes), answered by Simon Woods (12 votes)

—————————-

[How to riffle matrices] http://mathematica.stackexchange.com/questions/135848/how-to-riffle-matrices

I have four matrices

m = {{M11, M12, M13}, {M21, M22, M23}, {M31, M32, M33}};
n = {{N11, N12, N13}, {N21, N22, N23}, {N31, N32, N33}};
p = {{P11, P12, P13}, {P21, P22, P23}, {P31, P32, P33}};
q =  ...

- asked by Kowalski (8 votes), answered by Carl Woll (11 votes)

================================== Greatest hits from previous weeks: ==================================

[Is there an open source implementation of Mathematica-the-language?] http://mathematica.stackexchange.com/questions/4454/is-there-an-open-source-implementation-of-mathematica-the-language

I’ve seen questions before such as ”What is the best open-source equivalent for Mathematica?”, but that specific question (and that line of inquiry in general) cares more about the computer algebra ...

- asked by sblom (81 votes), answered by Simon (64 votes)

—————————-

[Is it possible to export the equations from Mathematica to MATLAB?] http://mathematica.stackexchange.com/questions/14035/is-it-possible-to-export-the-equations-from-mathematica-to-matlab

Is it possible to export the output expressions from Mathematica computations (e.g., equations) in valid MATLAB syntax?

- asked by Seyhmus Güngören (27 votes), answered by R. M. (35 votes)

================================== Can you answer these? ==================================

[Gap in X-axis when using LogLinearPlot] http://mathematica.stackexchange.com/questions/136025/gap-in-x-axis-when-using-loglinearplot

Basically, this is the plot that comes out when I choose

Frame -&gt; True

Due to my need of labeling the axes. Is there a way to get rid off of that annoying gap?

Here is the figure

Here is the  ...

- asked by Alan Turing (1 vote)

—————————-

[When solving a heavy PDE Mathematica falls out: what can be done] http://mathematica.stackexchange.com/questions/135819/when-solving-a-heavy-pde-mathematica-falls-out-what-can-be-done

I am solving a heavy PDE. The mesh is huge, and Mma falls out after few tens of minutes solving: the cell becomes inactive, kernel (pressumably) quits, all variables turn blue.

My question is, what ...

- asked by Alexei Boulbitch (3 votes)

—————————-

[Exporting Cellular Automata Image Sequence] http://mathematica.stackexchange.com/questions/136068/exporting-cellular-automata-image-sequence

I am trying to make an animation in Adobe After Effects utilizing cellular automata. I would like to export each step (say 500 steps) as a high resolution vector image so that I can combine them as an ...

- asked by Ryan Conover (1 vote)

35 Tuesday, January 17, 2017

==================================
Top new questions this week:
==================================

[How to rotate the curve but not the axes?] http://mathematica.stackexchange.com/questions/135376/how-to-rotate-the-curve-but-not-the-axes

I have a such graphic:

data = {{0, 5}, {1.9, 7.5}, {0, 12}, {-5, 15.5}, {-1.2, 33.4}};
p=Plot[Interpolation[Reverse /@ data, x, InterpolationOrder -&gt; 2], {x,
  0, 55}, Epilog -&gt; {Red,  ...

- asked by yode (11 votes), answered by kglr (11 votes)

—————————-

[Function to draw densely interconnected layers in graph (e.g., neural net)] http://mathematica.stackexchange.com/questions/135354/function-to-draw-densely-interconnected-layers-in-graph-e-g-neural-net

I can use Graph[] to manually draw the shape of a very simple set of interconnected layers (for instance, a small neural network):

Graph[{1 -&gt; 3, 2 -&gt; 3, 1 -&gt; 5, 2 -&gt; 5, 1 -&gt; 4, 2  ...

- asked by Larry OBrien (11 votes), answered by kglr (12 votes)

—————————-

[An Intersection function on lists that saves intersection positions] http://mathematica.stackexchange.com/questions/135583/an-intersection-function-on-lists-that-saves-intersection-positions

I would like an intersection function on lists like Intersection that also stores the coordinates of the intersections. For instance for a,b,c and b,c,e would give something like ...

- asked by Kvothe (9 votes), answered by ciao (9 votes)

—————————-

[Combining lists of lists with random structure] http://mathematica.stackexchange.com/questions/135238/combining-lists-of-lists-with-random-structure

I have two lists which I would like to combine. One is of a random structure, which might be:

l1={{3, 2, 4, 2}, {2, 3}, {4, 3}, {{2, 2}}, {{3, 3}}, {3, 2}}

where the elements in each sublist may ...

- asked by Jonathan Shock (9 votes), answered by Mr.Wizard (7 votes)

—————————-

[Slicing an Association with named key span without normalizing?] http://mathematica.stackexchange.com/questions/135092/slicing-an-association-with-named-key-span-without-normalizing

Is there way to slice an Association with named key span?

Span currently doesn’t accept named keys:

&lt;|"z" -&gt; 1, "x" -&gt; 2, "b" -&gt; 3, "a" -&gt; 4|&gt;  // Query["x" ;; "a"]

- asked by alancalvitti (9 votes), answered by Mr.Wizard (11 votes)

—————————-

[Finding Ramanujan’s taxicab numbers] http://mathematica.stackexchange.com/questions/135128/finding-ramanujans-taxicab-numbers

How to find Hardy-Ramanujan Numbers by using Mathematica?

Definition: Taxicab number is defined as the smallest number that can be expressed as a sum of two positive cubes in n  distinct ways. ...

- asked by vito (9 votes), answered by vito (6 votes)

—————————-

[Area of surface of revolution] http://mathematica.stackexchange.com/questions/135358/area-of-surface-of-revolution

I am asked to rotate the curve y = √4-−-x2   from x = − 1  to x = 1  about the x-axis and find the area of the surface. I was able to use RevolutionPlot3D to show the surface.

RevolutionPlot3D[Sqrt[4 ...

- asked by David (7 votes), answered by corey979 (10 votes)

================================== Greatest hits from previous weeks: ==================================

[Entering numbers in Scientific Notation?] http://mathematica.stackexchange.com/questions/36792/entering-numbers-in-scientific-notation

I need to play with a lot of powers such as 10^-3. 1E-3
does not work for it. Is there any short form for it?

- asked by hhh (23 votes), answered by Rahul (32 votes)

—————————-

[xkcd-style graphs] http://mathematica.stackexchange.com/questions/11350/xkcd-style-graphs

I received an email to which I wanted to respond with a xkcd-style graph, but I couldn’t manage it. Everything I drew looked perfect, and I don’t have enough command over PlotLegends to have these ...

- asked by Amatya (532 votes), answered by Simon Woods (385 votes)

================================== Can you answer these? ==================================

[Amelioration of a Karush-Kuhn-Tucker nice code] http://mathematica.stackexchange.com/questions/135220/amelioration-of-a-karush-kuhn-tucker-nice-code

In what concerns the resolution of a Karush-Kuhn-Tucker condition, this wonderful code borrowed to Parreiras (The Mathematica Journal 16 2014) which is a correction of another code by Kampas (The ...

- asked by cyrille.piatecki (4 votes)

—————————-

[URLDownload aborts prematurely] http://mathematica.stackexchange.com/questions/135355/urldownload-aborts-prematurely

So I’ve been trying to automate the download and build of various large packages for hooking Mathematica into extensions but the downloads continually finish prematurely.

Edit: first example was just ...

- asked by MB1965 (2 votes)

—————————-

[Simplify an integer expression involving Ceiling and Root[] of third degree polynomial] http://mathematica.stackexchange.com/questions/135566/simplify-an-integer-expression-involving-ceiling-and-root-of-third-degree-poly

I would like to simplify the following expression

    Ceiling[ToRadicals[Root[90 - 6 num + 65 #1 + 12 #1^2 + #1^3 &amp;, 1]]]

with num an integer greater than or equal to 16. I tried using ...

- asked by Piruzzolo (1 vote)

36 Tuesday, January 10, 2017

==================================
Top new questions this week:
==================================

[Is there any possibility to implement a structure like a ProgressIndicator into NDSolve?] http://mathematica.stackexchange.com/questions/134787/is-there-any-possibility-to-implement-a-structure-like-a-progressindicator-into

It is already formulated in the title. NDSolve takes sometimes a considerable piece of time. It would be very practical to have some information on how long it is still to wait. So, any ideas?

To ...

- asked by Alexei Boulbitch (20 votes), answered by user21 (16 votes)

—————————-

[This integral is divergent. How to use NIntegrate to see how it grows?] http://mathematica.stackexchange.com/questions/135073/this-integral-is-divergent-how-to-use-nintegrate-to-see-how-it-grows

I am trying to get information on the following integral:

∫ π−ϵ
      ----------∘-1--------------
 π−0.3(3+ cos x)  (3+ cosx)2 − 4

The lower limit is somewhat arbitrary; the point is that ...

- asked by Gelasio Salazar (10 votes), answered by Michael E2 (6 votes)

—————————-

[Call a Haskell DLL from Mathematica] http://mathematica.stackexchange.com/questions/134913/call-a-haskell-dll-from-mathematica

Looking for a way to call a Haskell DLL from Mathematica, I’ve stumbled on this, for GNU R:

http://neilmitchell.blogspot.com.br/2011/10/calling-haskell-from-r.html

It is (to me) a beautiful example ...

- asked by Rand (10 votes), answered by WReach (11 votes)

—————————-

[Product of set elements not exceeding a bound] http://mathematica.stackexchange.com/questions/134743/product-of-set-elements-not-exceeding-a-bound

I have a set of distinct positive integers l (if you wish, you may assume it is a list ordered by size), and a bound lim. In general, l has thousands of elements, but all are at most equal to lim. I ...

- asked by rogerl (10 votes), answered by george2079 (4 votes)

—————————-

[How does Mathematica solve a certain differential equation?] http://mathematica.stackexchange.com/questions/135055/how-does-mathematica-solve-a-certain-differential-equation

I was trying to solve a nonlinear differential equation with the following code.

DSolve[3*x^2/D[u[x, y], x] + 3*y^2/D[u[x, y], y] == -1, u, {x, y}]


And I got the following output:

{{u -&gt;  ...

- asked by usr109876787 (8 votes), answered by Michael E2 (12 votes)

—————————-

[How to cross-compile LibraryLink code for multi-platform distribution] http://mathematica.stackexchange.com/questions/135022/how-to-cross-compile-librarylink-code-for-multi-platform-distribution

I am running Mathematica on a Windows 10 machine and I would like to develop a package for public distribution. Most of the package will be Mathematica code, but some timing-critical parts should be ...

- asked by Ben Niehoff (8 votes)

—————————-

[Plotting difference between two Half Normal Distributions] http://mathematica.stackexchange.com/questions/134824/plotting-difference-between-two-half-normal-distributions

I am new to Mathematica, and this question may reflect that.

I am trying to plot the probability density function of a random variable which equals the difference between two independent random ...

- asked by user120911 (8 votes), answered by Jim Baldwin (9 votes)

================================== Greatest hits from previous weeks: ==================================

[How to create a fascinating QR code like this?] http://mathematica.stackexchange.com/questions/120041/how-to-create-a-fascinating-qr-code-like-this

Check the facinating QRCode in my profile page here

You can find that this QRCode is some sort of intriguing as the QRCode is a IMAGE ITSELF!!!

So my question is, how to create such a QRCode ...

- asked by Wjx (24 votes), answered by Wjx (19 votes)

—————————-

[Find the 5566th digit after the decimal point of 7/101] http://mathematica.stackexchange.com/questions/125025/find-the-5566th-digit-after-the-decimal-point-of-7-101

I want to find the 5566th digit after the decimal point of 7/101. I input the following code into Mathematica 11:

Mod[IntegerPart[7/101*10^5566], 10]

The output is 6, which is the correct answer. ...

- asked by Wei-Cheng Liu (17 votes), answered by yarchik (19 votes)

================================== Can you answer these? ==================================

[Inset thickness and ImageResolution] http://mathematica.stackexchange.com/questions/134738/inset-thickness-and-imageresolution

I have noticed that when I export something with an Inset objects,

pp[t_] :=
  Plot[Sin[x], {x, -10, 10},
    Epilog -&gt;
      {Inset[
         Framed[
           Text[Style[HoldForm["t=" t],  ...

- asked by usumdelphini (4 votes)

—————————-

[Find the parameter values for my matrix for it to have imaginary eigenvalues] http://mathematica.stackexchange.com/questions/134909/find-the-parameter-values-for-my-matrix-for-it-to-have-imaginary-eigenvalues

Say I have a matrix that depends on a parameter u  . The following may be an example:

a = {{1, u^3 + 2, 1}, {0, 1, u}, {1/u^2, 0, 1}};

My real problem is 12x12 matrix with difficult parametric ...

- asked by Mirko Aveta (1 vote)

—————————-

[NotebookEvaluate breaks notebook’s context] http://mathematica.stackexchange.com/questions/135025/notebookevaluate-breaks-notebooks-context

Here is an example of a notebook with local context:

nb = CreateDocument[{
  ExpressionCell[Defer @ CurrentValue[EvaluationNotebook[], CellContext], "Input"],
  ExpressionCell[Defer @ $Context,  ...

- asked by Kuba (2 votes)

37 Tuesday, January 3, 2017

==================================
Top new questions this week:
==================================

[Why should I avoid the For loop in Mathematica?] http://mathematica.stackexchange.com/questions/134609/why-should-i-avoid-the-for-loop-in-mathematica

Some people advise against the use of For loops in Mathematica. Why? Should I heed this advice? What is wrong with For? What should I use instead?

- asked by Szabolcs (27 votes), answered by Szabolcs (36 votes)

—————————-

[Is there a style sheet that can be used to generate Stack Exchange input?] http://mathematica.stackexchange.com/questions/134518/is-there-a-style-sheet-that-can-be-used-to-generate-stack-exchange-input

It would be convenient if there were a style sheet that automatically indented input cells, and automatically commented output cells, so that one could generate a stack exchange response in WL, and ...

- asked by Carl Woll (24 votes), answered by Carl Woll (21 votes)

—————————-

[Function to create a path made of horizontal and vertical lines between a number of points] http://mathematica.stackexchange.com/questions/134424/function-to-create-a-path-made-of-horizontal-and-vertical-lines-between-a-number

I would like to create a function where I can define which case I want to use to create a path.

p1 = {40, 48}; p2 = {50, 116}; p3 = {63, 160};
listPurple = Symbol["p" &lt;&gt; ToString[#]] &amp; /@  ...

- asked by Maria Regina (16 votes), answered by corey979 (15 votes)

—————————-

[How to wrap a crumpled paper over a surface?] http://mathematica.stackexchange.com/questions/134514/how-to-wrap-a-crumpled-paper-over-a-surface

My initial question was about the making of a crumpled paper. After reading this article suggested by J.M. and little more browsing (kind of random walk you do on a Saturday) I thought about expanding ...

- asked by Sumit (8 votes)

—————————-

[Would like input and output printed on same line, w/o needing extra syntax] http://mathematica.stackexchange.com/questions/134406/would-like-input-and-output-printed-on-same-line-w-o-needing-extra-syntax

SUMMARY

I’d like to get MMA to automatically print both input and output on the same line, in TraditionalForm, without having to add any extra syntax. Further, I’d like the output to be fully ...

- asked by theorist (8 votes), answered by Simon Rochester (4 votes)

—————————-

[Issue with Cell Frames in version 11] http://mathematica.stackexchange.com/questions/134665/issue-with-cell-frames-in-version-11

Since upgrading to version 11, all of my notebooks now have cell frames are either missing the top or bottom part. Is anyone else experiencing this? Is there a way to fix this? Is this considered ...

- asked by Michael McCain (7 votes), answered by MB1965 (5 votes)

—————————-

[How to speed up this code about a triple integral?] http://mathematica.stackexchange.com/questions/134477/how-to-speed-up-this-code-about-a-triple-integral

How to speed up this code? It’s unbelievably slow!!! My solution with pen and paper is faster.

Clear[R, h];
Integrate[
 Integrate[
  Integrate[1, {z, h, Sqrt[R^2 - x^2 - y^2]},
   Assumptions -&gt;  ...

- asked by Mika Ike (7 votes), answered by corey979 (10 votes)

================================== Greatest hits from previous weeks: ==================================

[Exporting graphics to PDF - huge file] http://mathematica.stackexchange.com/questions/1542/exporting-graphics-to-pdf-huge-file

I want to draw some basic surfaces, export them to PDF and include them in a LaTeX file. I create a simple 3D graphics object, for instance with

 ParametricPlot3D[{r Cos[θ], r Sin[θ], r^2}, {r, 0,  ...

- asked by Matthew Leingang (89 votes), answered by Heike (75 votes)

—————————-

[Entering numbers in Scientific Notation?] http://mathematica.stackexchange.com/questions/36792/entering-numbers-in-scientific-notation

I need to play with a lot of powers such as 10^-3. 1E-3 does not work for it.
Is there any short form for it?

- asked by hhh (21 votes), answered by Rahul (30 votes)

================================== Can you answer these? ==================================

[How to specify halting states when using function TuringMachine?] http://mathematica.stackexchange.com/questions/134628/how-to-specify-halting-states-when-using-function-turingmachine

The function TuringMachine generates a list that represents the evolution of a Turing Machine given a rule that specifies its behaviour (i.e. set of instructions).

For example, the following rule ...

- asked by Lili (4 votes)

—————————-

[Can I use Mathematica for the symbolic verification of cases of a general problem?] http://mathematica.stackexchange.com/questions/134515/can-i-use-mathematica-for-the-symbolic-verification-of-cases-of-a-general-proble

I have never used Mathematica before, but I am contemplating using it to solve this problem for a simple case of f(x) = C,1 < x < 2  and = 0  and = 0  . I can easily get ˆf , the Fourier transform of ...

- asked by Rajesh Dachiraju (2 votes)

—————————-

[Antialiasing in Plot3D doesn’t work well] http://mathematica.stackexchange.com/questions/134612/antialiasing-in-plot3d-doesnt-work-well

My code is very simple:

Style[Plot3D[Cos[x + 0*y], {x, -10, 10}, {y, -2, 42}, Mesh -&gt; None],
  Antialiasing -&gt; True]

There seems some ripple on the top of the figure and I doubt whether it ...

- asked by user29114 (1 vote)

38 Tuesday, December 27, 2016

==================================
Top new questions this week:
==================================

[Partitioning a number into consecutive integers] http://mathematica.stackexchange.com/questions/134252/partitioning-a-number-into-consecutive-integers

Consider n=45; then

1+ 2 + 3+ 4 + 5+  6+ 7 + 8+ 9 = 45
5 + 6 + 7+ 8 + 9+ 10 = 45
7+ 8 + 9+  10+ 11 = 45
14+ 15 + 16 = 45
22 + 23 = 45

Question: how to find all representations of a given positive integer n as a sum of ...

- asked by corey979 (17 votes), answered by corey979 (19 votes)

—————————-

[Why is my GIF shaky?] http://mathematica.stackexchange.com/questions/134272/why-is-my-gif-shaky

As you can see, the circles are shaking vertically as they approaching each other. Why is that?

The code:

g = Table[
    Graphics[{Thickness[0.01],
             Table[{ Circle[{0 + x, 0}, r],  ...

- asked by Jason (13 votes), answered by Sumit (10 votes)

—————————-

[Can Mathematica edit large binary files in-place?] http://mathematica.stackexchange.com/questions/133973/can-mathematica-edit-large-binary-files-in-place

I have a very large binary data file (several hundred GB) which I would like to edit using Mathematica. The only edits required are a few isolated byte replacements—no insertions or deletions. Is it ...

- asked by David Zhang (12 votes)

—————————-

[Solving chess bishop problem] http://mathematica.stackexchange.com/questions/134218/solving-chess-bishop-problem

I have generalized the problem in this way where I have a list

list=Tuples[Range[8],2]

I want to find the largest sublist in which the addition of the two entries for any two elements of the ...

- asked by m. bubu (10 votes), answered by ubpdqn (11 votes)

—————————-

[How to get such rule with a elegant method] http://mathematica.stackexchange.com/questions/134227/how-to-get-such-rule-with-a-elegant-method

I have two lists:

list={{1,2,3,5},{5,3,9,11,12},{5,9,10,16}};
list2={{7,89},{96,5},{-6,-98}};

This is the expected result.


{{1-&gt;{7,89},2-&gt;{7,89},3-&gt;{7,89},5-&gt;{7,89}},
  ...

- asked by yode (9 votes), answered by Mr.Wizard (9 votes)

—————————-

[Pseudo-currying in one line] http://mathematica.stackexchange.com/questions/134315/pseudo-currying-in-one-line

Often when I’m writing OOP code using an object-manager association I find myself doing something akin to currying the arguments to some form of delegate object or head. (Building a one-argument ...

- asked by MB1965 (8 votes), answered by Bob Hanlon (8 votes)

—————————-

[How to create a multi-graphics plot (i.e. the decomposition of phase plane portrait) with well-organized structure?] http://mathematica.stackexchange.com/questions/134228/how-to-create-a-multi-graphics-plot-i-e-the-decomposition-of-phase-plane-portr

Background

I am trying to create a three-graphics plot using the command GraphicsGrid[] to show the decomposition of the phase plane portrait; unfortunately, the plot created is very ugly since the ...

- asked by Liang.X (8 votes), answered by Sumit (8 votes)

================================== Greatest hits from previous weeks: ==================================

[Finding Limits in several variables] http://mathematica.stackexchange.com/questions/21544/finding-limits-in-several-variables

Is there a way to find a limit of a multivariable function, like

(x,ly)im→ (0,0)f (x,y )
with Mathematica?

When f  is continuous, we can use

(x,lyi)→m(0,0)
...

- asked by Dominic Michaelis (21 votes), answered by whuber (32 votes)

—————————-

[Can Mathematica do symbolic linear algebra?] http://mathematica.stackexchange.com/questions/3242/can-mathematica-do-symbolic-linear-algebra

For instance, is there some way I can say ”let A and B be arbitrary real m × n  and k × m  matrices, Simplify[Transpose[Transpose[A].Transpose[B]]]” and Mathematica would simplify it to B.A? ...

- asked by nikie (38 votes), answered by helen (19 votes)

================================== Can you answer these? ==================================

[Graph that shows how symbols are used in an expression] http://mathematica.stackexchange.com/questions/134180/graph-that-shows-how-symbols-are-used-in-an-expression

I would like to make a graph to show how symbols build up an expression. For example, the matrix multiplication

$$
\left(
\begin{array}{ccc}
 a &amp; b &amp; c \\
 d &amp; e &amp; f \\
\end{array}
 ...

- asked by ConvexMartian (4 votes)

—————————-

[Question about DynamicModule] http://mathematica.stackexchange.com/questions/134063/question-about-dynamicmodule

I have a such custom function:

MyCopy := DynamicModule[{from, to},
  Print@Grid[{{FileNameSetter[Dynamic[from], "Directory"],
      Dynamic[from]}, {FileNameSetter[Dynamic[to], "Directory"],
       ...

- asked by yode (3 votes)

—————————-

[General solution of inscribed square problem] http://mathematica.stackexchange.com/questions/134237/general-solution-of-inscribed-square-problem

There is my earlier question about Inscribed square problem

Now I tried to find the general solution for any curve f(x,y) = 0  .

For instance :

(x2 + y2 − 1)3 − x2y3 = 0

...

- asked by vito (5 votes)

39 Tuesday, December 20, 2016

==================================
Top new questions this week:
==================================

[How can I work with RawArray?] http://mathematica.stackexchange.com/questions/133666/how-can-i-work-with-rawarray

RawArray seems to be able to efficiently hold integer and floating point data of various sizes.

What is RawArray good for? How can we use it?

- asked by Szabolcs (19 votes), answered by Szabolcs (15 votes)

—————————-

[Random points around the given curve] http://mathematica.stackexchange.com/questions/133682/random-points-around-the-given-curve

How to plot a random points around the following Helix curve?

 ParametricPlot3D[{6 Cos[t], 6 Sin[t], t}, {t, -2 π, 4 π},
 PlotTheme -&gt; "Detailed", PlotStyle -&gt; {Blue, Thickness[Large]},
  ...

- asked by vito (14 votes), answered by J. M. (15 votes)

—————————-

[Intuition behind FoldPair and SequenceFold?] http://mathematica.stackexchange.com/questions/133625/intuition-behind-foldpair-and-sequencefold

In trawling through the documentation I’ve found the functions FoldPairList and SequenceFoldList. Examples are given of how to use FoldPairList:

Partition a list into sublists of different lengths ...

- asked by pdmclean (12 votes), answered by andre (4 votes)

—————————-

[Product of two lists] http://mathematica.stackexchange.com/questions/133723/product-of-two-lists

Please, for the two lists:

L1 := {{a, b}, {c, d}, {e, f}}
L2 := {{g, h, i}, {j, k, q}}


I need the result

{{{a g, a h, a i}, {c g, c h, c i}, {e g, e h, e i}},
 {{b j, b k, b q}, {d j, d k, d  ...

- asked by Ali (11 votes), answered by xzczd (13 votes)

—————————-

[Is there something similar to seaborn stripplot in mathematica] http://mathematica.stackexchange.com/questions/133634/is-there-something-similar-to-seaborn-stripplot-in-mathematica

Is there something similar to seaborn stripplot in mathematica? The graph I am trying to make is like this:

- asked by Yordan (11 votes), answered by Brett Champion (12 votes)

—————————-

[Collapsible Tree] http://mathematica.stackexchange.com/questions/133492/collapsible-tree

Has somebody tried to program for data visualization an interactive Collapsible Tree like shown here: http://bl.ocks.org/mbostock/4339083. This implements the Reingold-Tilford algorithm.

...

- asked by mrz (8 votes)

—————————-

[FindDistributionParameters fails with custom distribution which cannot be evaluated symbolically] http://mathematica.stackexchange.com/questions/133456/finddistributionparameters-fails-with-custom-distribution-which-cannot-be-evalua

Context

I am interested in measuring the dark energy equation of state of the universe while fitting the PDF of density in cells. This involves fitting a one parameter PDF to some data.

Following ...

- asked by chris (7 votes)

================================== Greatest hits from previous weeks: ==================================

[How can I draw the Olympic rings with Mathematica?] http://mathematica.stackexchange.com/questions/8885/how-can-i-draw-the-olympic-rings-with-mathematica

How can I draw the 5 interlocking Olympic rings with Mathematica?

(SVG version)

Edit

Hard choice, but some pretty cool answers here. I didn’t have 3D answers in mind when I posted the question, ...

- asked by Mike Honeychurch (42 votes), answered by cormullion (19 votes)

—————————-

[Where can I find examples of good Mathematica programming practice?] http://mathematica.stackexchange.com/questions/18/where-can-i-find-examples-of-good-mathematica-programming-practice

I consider myself a pretty good Mathematica programmer, but I’m always looking out for ways to either improve my way of doing things in Mathematica, or to see if there’s something nifty that I haven’t ...

- asked by J. M. (448 votes), answered by faysou (397 votes)

================================== Can you answer these? ==================================

[Symbolic Weak Form] http://mathematica.stackexchange.com/questions/133575/symbolic-weak-form

Usually I write the weak form by hand for my FEM code, but it’s a little annoying and mechanic sometimes.

So, I wonder, is there any way to generate the symbolic weak form in Mathematica? For ...

- asked by senseiwa (5 votes)

—————————-

[Why is Minimize spinning?] http://mathematica.stackexchange.com/questions/133789/why-is-minimize-spinning

The command

Minimize[a^2 + b^2 + c^2 + a*b + b*c + a*c -
(a + b - c)*Sqrt[2 a*b + b*c + a*c] - (b + c - a)* Sqrt[2 b*c + b*a + a*c] -
(a + c - b)*Sqrt[2 a*c + a*b + b*c], a &gt;= 0 &amp;&amp; b  ...

- asked by user64494 (4 votes)

—————————-

[How to export an MXNet?] http://mathematica.stackexchange.com/questions/133857/how-to-export-an-mxnet

I was hoping there was some way to generate the .params and .json file needed to define an MXNet model, from a network trained using NetTrain[] in Mathematica:

I see these functions in the ...

- asked by user5601 (5 votes)

40 Tuesday, December 13, 2016

==================================
Top new questions this week:
==================================

[Query: adding additional operator changes meaning of preceding operators] http://mathematica.stackexchange.com/questions/133124/query-adding-additional-operator-changes-meaning-of-preceding-operators

Consider the following query:

Range[5] // Query[Select[EvenQ] /* Append[1], f]

(* {f[2], f[4], 1} *)

It selects the even numbers, applies f to them and finally appends 1 to the list. As expected, ...

- asked by WReach (15 votes), answered by WReach (15 votes)

—————————-

[Why does Mathematica think this series doesn’t converge?] http://mathematica.stackexchange.com/questions/132982/why-does-mathematica-think-this-series-doesnt-converge

Bug introduced in 10.0 and persisting through 11.0 (reported as CASE:3790525)

Here’s a simple series:

Sum[t^k DiscreteDelta[k]/k!,{k,0,Infinity}]

Mathematica says that it doesn’t converge. But ...

- asked by Ruslan (13 votes), answered by Jules Lamers (9 votes)

—————————-

[Joining two lists with relational operators] http://mathematica.stackexchange.com/questions/132928/joining-two-lists-with-relational-operators

I have two lists liste = {x, -y, y, -z} and
listv = {1, -2, 3, -4}, which represent the inequities
obtained evaluating liste - listv &lt;= 0. How do I reassemble or
join those two separate lists into  ...

- asked by nanjun (13 votes), answered by Kuba (15 votes)

—————————-

[What assumptions do I need to make Mathematica integrate a function?] http://mathematica.stackexchange.com/questions/133052/what-assumptions-do-i-need-to-make-mathematica-integrate-a-function

When I feed Mathematica the following integral:

Integrate[Sqrt[(A - x) (B - x)/x], {x, 0, B}]

it spits it back out without evaluating it. However, it can evaluate the integral

Integrate[Sqrt[(2 -  ...

- asked by user45146 (11 votes), answered by Artes (12 votes)

—————————-

[Do Apple Watch + Mathematica integrations still work?] http://mathematica.stackexchange.com/questions/133358/do-apple-watch-mathematica-integrations-still-work

I tried to follow this blog post: Instant Apps for Apple Watch, but none of the examples given worked, instead, they would simply hang on the ”loading” screen.

Can anyone verify if this ...

- asked by M.R. (9 votes)

—————————-

[Locate Start and End Positions of Repeated Sequences in a list] http://mathematica.stackexchange.com/questions/133164/locate-start-and-end-positions-of-repeated-sequences-in-a-list

ListA = 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 12, 12, 12, 14, 14, 14, 12, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, ...

- asked by SPIL (8 votes), answered by Suba Thomas (5 votes)

—————————-

[How can I add noise to a neural network input?] http://mathematica.stackexchange.com/questions/133090/how-can-i-add-noise-to-a-neural-network-input

A common ”trick” in neural network training is to train an autoencoder using a ”degraded” sample as input and the original sample as target output. The layer type DropoutLayer[] is made for this ...

- asked by nikie (8 votes), answered by nikie (5 votes)

================================== Greatest hits from previous weeks: ==================================

[Can Mathematica do symbolic linear algebra?] http://mathematica.stackexchange.com/questions/3242/can-mathematica-do-symbolic-linear-algebra

For instance, is there some way I can say ”let A and B be arbitrary real m × n  and k × m  matrices, Simplify[Transpose[Transpose[A].Transpose[B]]]” and Mathematica would simplify it to B.A? ...

- asked by nikie (38 votes), answered by helen (19 votes)

—————————-

[Calculate the 2D Fourier transform of an Image] http://mathematica.stackexchange.com/questions/29203/calculate-the-2d-fourier-transform-of-an-image

I am new to Mathematica, and using version 8.0.

I would like to calculate the 2D Fourier Transform of an Image with Mathematica and plot the magnitude and phase spectrum, as well as reconstruct the ...

- asked by user8727 (5 votes), answered by Nasser (27 votes)

================================== Can you answer these? ==================================

[Mathematica script, called from Windows task scheduler, does not export graphics] http://mathematica.stackexchange.com/questions/133075/mathematica-script-called-from-windows-task-scheduler-does-not-export-graphics

When I run the following script from command line,

Needs["JLink`"];
ConnectToFrontEnd[];
resultChart = UseFrontEnd[JuliaSetPlot[0.365 - 0.37 I]];
UseFrontEnd[Export["test.png", resultChart]];

...

- asked by Karsten W. (2 votes)

—————————-

[Is it possible to do matrix algebra symbolically?] http://mathematica.stackexchange.com/questions/132955/is-it-possible-to-do-matrix-algebra-symbolically

I’m reading a book that has the following theorem:

I am trying to make Mathematica perform these calculations for me. Is it possible to do it without having to declare the matrices? For ...

- asked by Oppa Hilbert Style (2 votes)

—————————-

[Making graphic objects disappear interactively] http://mathematica.stackexchange.com/questions/133256/making-graphic-objects-disappear-interactively

I am trying to create a program where dots on a plane disappear when an object passes over them. I am using EventHandler to code the arrow keys for control of the object. I want each dot to ...

- asked by Savannah S (1 vote)

41 Tuesday, December 6, 2016

==================================
Top new questions this week:
==================================

[How to find arXiv articles] http://mathematica.stackexchange.com/questions/132685/how-to-find-arxiv-articles

I found at Twitter that is possible to search for arXiv articles with Mathematica:

E.g. the following code:

arXiv = ServiceConnect["ArXiv"];

articles = arXiv["Search", {"Query" -&gt;  ...

- asked by mrz (16 votes), answered by user21 (11 votes)

—————————-

[Find lane lines] http://mathematica.stackexchange.com/questions/132443/find-lane-lines

A crucial step in self-driving car is to detect lane lines. I’m wondering whether this can be achieved robustly using Mathematica’s rich image processing tools.

For example how can I take camera ...

- asked by xslittlegrass (14 votes), answered by nikie (14 votes)

—————————-

[Neural Network for polynomial fit] http://mathematica.stackexchange.com/questions/132546/neural-network-for-polynomial-fit

I’m trying to build up a neural network with Mathematica 11.0, that should fit data which behaves like a polynom of third order. I thought that an NN with one or two hidden layers can fit any ...

- asked by A.Zachl (12 votes), answered by nikie (9 votes)

—————————-

[How to make notebooks suitable for the Documentation Center?] http://mathematica.stackexchange.com/questions/132392/how-to-make-notebooks-suitable-for-the-documentation-center

Normally, documentation meant to be integrated into the Documentation Center is built from special source notebooks.

According to the Workbench documentation, it should also be possible to use ...

- asked by Szabolcs (12 votes), answered by jkuczm (5 votes)

—————————-

[Largest palindrome from given string] http://mathematica.stackexchange.com/questions/132834/largest-palindrome-from-given-string

Someone recently posted a request on LinkedIn for an algorithm to find the largest palindrome from a given string.

I came up with this, which I believe does the trick, but I am wondering if there ...

- asked by Jonathan Kinlay (10 votes), answered by Kuba (10 votes)

—————————-

[Why Function is not identical to `&` in autocompilation?] http://mathematica.stackexchange.com/questions/132656/why-function-is-not-identical-to-in-autocompilation

Here is the example, copied from here

square = Function[x, x^2];
square1 = #^2 &amp;;

the timing and unpacking status shows

data = RandomReal[0, 10, 10000];

...

- asked by matheorem (10 votes), answered by m_goldberg (4 votes)

—————————-

[Analytic solution to Newtonian gravity differential equation] http://mathematica.stackexchange.com/questions/132875/analytic-solution-to-newtonian-gravity-differential-equation

I was told that I could obtain an analytic solution to a particle falling under the influence of Newtonian gravity by using DSolveValue.

What I am given

G  = M  = m =  1  M  is a point mass at z = 0  ...

- asked by Joe (9 votes), answered by Kagaratsch (9 votes)

================================== Greatest hits from previous weeks: ==================================

[Unit Discovery: Is this some sort of a sick joke?] http://mathematica.stackexchange.com/questions/124745/unit-discovery-is-this-some-sort-of-a-sick-joke

Alright, let’s have some fun here. I am essentially following the documentation by Wolfram, just looking at different quantities.

N[UnitConvert[Quantity["earths gravity"]]]

9.80665m/(s)^2

Hmm, ...

- asked by Pirx (30 votes), answered by xavier (30 votes)

—————————-

[How can Mathematica be used to create images like these?] http://mathematica.stackexchange.com/questions/118992/how-can-mathematica-be-used-to-create-images-like-these

Here are two examples of artistic image interpolation using just black lines:

TRIANGULATION: ANGULAR CELEBRITIES DRAWN WITH A PEN Interpolation for Triangulation-represented Digital Image

The ...

- asked by R Hall (28 votes), answered by MarcoB (29 votes)

================================== Can you answer these? ==================================

[How to find a value to make function positive and real?] http://mathematica.stackexchange.com/questions/132883/how-to-find-a-value-to-make-function-positive-and-real

Let

x=(((-3 + r) r^2 + a^2 (1 + r)) Csc[θ])/(a (-1 + r))

y=Sqrt[(a^2 (a^2 (1 + r)^2 + 2 r^2 (-3 + r^2)) +
 a^4 (-1 + r)^2 Cos[θ]^2 - ((-3 + r) r^2 +
    a^2 (1 + r))^2 Csc[θ]^2)/(a^2 (-1 + r)^2)]

...

- asked by MrDi (1 vote)

—————————-

[Creating an automatic code feedback for class] http://mathematica.stackexchange.com/questions/132880/creating-an-automatic-code-feedback-for-class

I’m trying to create a server application that accepts uploaded Mathematica files (that follow a certain API), then run a few tests on modules defined within those files. This is for a course where ...

- asked by michael99man (1 vote)

—————————-

[Nontrivial background removal] http://mathematica.stackexchange.com/questions/132844/nontrivial-background-removal

I have an image of a product on a poorly made green screen and need to segment out just the product:

The problem is that it contains a mirror, so simple color-based methods are not enough.

I tried ...

- asked by M.R. (4 votes)

42 Tuesday, November 29, 2016

==================================
Top new questions this week:
==================================

[PacletInfo.m documentation project] http://mathematica.stackexchange.com/questions/132064/pacletinfo-m-documentation-project

Packages can be made into paclets, which provides easy distribution and versioning. The paclet metadata is in the PacletInfo.m file. The PacletInfo settings also determine how the paclet can extend ...

- asked by Szabolcs (25 votes), answered by Szabolcs (22 votes)

—————————-

[Replace custom functions, leave built in functions untouched?] http://mathematica.stackexchange.com/questions/131938/replace-custom-functions-leave-built-in-functions-untouched


I have three expressions a[x, y], b[x, y], c[x, y] that act as
placeholders for functions of two variables x,y. Consider the following substitution:

a[x, y]/(b[x, y] c[x, y]) /. f_[x1_, y1_] :&gt;  ...

- asked by Kagaratsch (16 votes), answered by Mr.Wizard (18 votes)

—————————-

[Why CompilationTarget -¿ C is slower than directly writing with C?] http://mathematica.stackexchange.com/questions/132130/why-compilationtarget-c-is-slower-than-directly-writing-with-c

Probably a hard question, but I think it’s better to cry out loud.

I’ve hesitated for a while about whether I should post this in StackOverflow with a c tag or not, but finally decide to keep it ...

- asked by xzczd (15 votes), answered by Albert Retey (11 votes)

—————————-

[Detecting kernel initialization] http://mathematica.stackexchange.com/questions/132212/detecting-kernel-initialization

Certain operations do not work during kernel initialization. Code from Kernel/init.m, the Autoload directory, or packages set to autoload may evaluate at initialization time.

Is there a way to ...

- asked by Szabolcs (12 votes), answered by Szabolcs (10 votes)

—————————-

[How can I change the default file type for ”Save Selection As”] http://mathematica.stackexchange.com/questions/132224/how-can-i-change-the-default-file-type-for-save-selection-as

When using the menu item File - Save Selection As, the default file type is PDF. Is there any way to change the default to something else, for example PNG?

- asked by Simon Woods (12 votes), answered by Mike Honeychurch (13 votes)

—————————-

[How to obtain the ViewPoint] http://mathematica.stackexchange.com/questions/132228/how-to-obtain-the-viewpoint

Normally, I used ViewPoint in the code in Plot3D. Most of the time, I will use mouse to rotate the 3D object to get a better view point. The problem is, when I find the best view point for me, is ...

- asked by Qi Zhong (12 votes), answered by Jack LaVigne (14 votes)

—————————-

[Wonky Solutions to Schrödinger Equation with Box Barrier] http://mathematica.stackexchange.com/questions/131854/wonky-solutions-to-schr%C3%B6dinger-equation-with-box-barrier

I’m trying to solve the Schrödinger equation using NDSolve in a case where there is a potential box barrier. The initial condition is a cosine wave, and for boundary conditions I require that the ...

- asked by Buddhapus (8 votes), answered by xzczd (4 votes)

================================== Greatest hits from previous weeks: ==================================

[Can Mathematica do symbolic linear algebra?] http://mathematica.stackexchange.com/questions/3242/can-mathematica-do-symbolic-linear-algebra

For instance, is there some way I can say ”let A and B be arbitrary real m × n  and k × m  matrices, Simplify[Transpose[Transpose[A].Transpose[B]]]” and Mathematica would simplify it to B.A? ...

- asked by nikie (35 votes), answered by helen (18 votes)

—————————-

[How to tell Mathematica that certain variables are real/imaginary, integer-valued, etc] http://mathematica.stackexchange.com/questions/66273/how-to-tell-mathematica-that-certain-variables-are-real-imaginary-integer-value

I’m trying to expedite some quantum mechanical calculations by running them through Mathematica. Expectation values and stuff like that. When I say, for example,

u[x_] := Sqrt[2/L] * Sin[Pi * n * x /  ...

- asked by Matthew Brunetti (9 votes), answered by SquareOne (7 votes)

================================== Can you answer these? ==================================

[Is it possible to change the text cursor’s shape and color?] http://mathematica.stackexchange.com/questions/132322/is-it-possible-to-change-the-text-cursors-shape-and-color

I find it visually pleasant to reverse the background and foreground colors when working on a notebook; as shown below, in fact, it’s almost a requirement after working long hours on the same ...

- asked by Jerome Ibanes (1 vote)

—————————-

[FindClusters doesn’t accept custom DistanceFunction] http://mathematica.stackexchange.com/questions/132287/findclusters-doesnt-accept-custom-distancefunction

I have a problem with using custom DistanceFunction in FindClusters. To make the issue as simple as possible, consider clustering odd &amp; even numbers in the following way:

...

- asked by ahrvoje (6 votes)

—————————-

[FrameLabel is Broken for ArrayPlot and MatrixPlot] http://mathematica.stackexchange.com/questions/132008/framelabel-is-broken-for-arrayplot-and-matrixplot

In version 11.0.1 the documentation for FrameLabel states its format is

left, right, bottom, top

However, it appears that this is not the case for MatrixPlot.

...

- asked by Edmund (5 votes)

43 Tuesday, November 22, 2016

==================================
Top new questions this week:
==================================

[Create the source image for this cool animated illusion] http://mathematica.stackexchange.com/questions/131644/create-the-source-image-for-this-cool-animated-illusion

Have a look at this very awesome video:

https://www.youtube.com/watch?v=lvvcRdwNhGM

You have a vertically discretized image, which is composed of 5 or 6 images, which are shifted by an increment, as ...

- asked by DoHe (22 votes), answered by corey979 (25 votes)

—————————-

[Restarting Mathematica automatically] http://mathematica.stackexchange.com/questions/131573/restarting-mathematica-automatically

I run a large computation in a loop. At each cycle of the loop I produce large arrays that I save on a disk. At each cycle I would like to Quit Mathematica and then restart automatically, loading ...

- asked by Vadim (15 votes), answered by Szabolcs (14 votes)

—————————-

[How to handle package dependencies?] http://mathematica.stackexchange.com/questions/131567/how-to-handle-package-dependencies

When an application written in C++ depends on some libraries, the libraries are usually shipped together with the application. Two applications that depend on the same library will not share the same ...

- asked by Szabolcs (11 votes), answered by Kuba (3 votes)

—————————-

[How to sample many points below a curve?] http://mathematica.stackexchange.com/questions/131755/how-to-sample-many-points-below-a-curve

I have plotted the curve, and I wanted to take 1000 points in the shaded area uniformly. How can I make it?

Plot[1/π Cos[θ]^2, {θ, 0, 2 π}, Filling -&gt; Bottom]

- asked by ZHANG Juenjie (10 votes), answered by bbgodfrey (11 votes)

—————————-

[how to style multi-value interpolation function plot?] http://mathematica.stackexchange.com/questions/131516/how-to-style-multi-value-interpolation-function-plot

Is there a cleaner way to apply different styles to the different channels of a multi value interpolation function?

here is a 2-output interpolation function:

f = Interpolation[Table[ {x, N@{Sin[x],  ...

- asked by george2079 (10 votes), answered by Michael E2 (7 votes)

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[Backtesting a Probability of Default (PD) model] http://mathematica.stackexchange.com/questions/131347/backtesting-a-probability-of-default-pd-model

Background

PD models

Financial institutions use Probability of Default (PD) models for various purposes such as client acceptance, provisioning and regulatory capital calculation as required by the ...

- asked by Sjoerd C. de Vries (10 votes), answered by Sjoerd C. de Vries (14 votes)

—————————-

[Display bug in Dataset’s UnitConvert handling] http://mathematica.stackexchange.com/questions/131332/display-bug-in-datasets-unitconvert-handling

Bug introduced in 11.0.1 (or possibly 11.0.0)

Is this yet another annoying regression in v11 Dataset type handling? The display form seems to be a formatting bug:

The numerator and denominator of ...

- asked by alancalvitti (10 votes), answered by WReach (4 votes)

================================== Greatest hits from previous weeks: ==================================

[Exporting graphics to PDF - huge file] http://mathematica.stackexchange.com/questions/1542/exporting-graphics-to-pdf-huge-file

I want to draw some basic surfaces, export them to PDF and include them in a LaTeX file. I create a simple 3D graphics object, for instance with

 ParametricPlot3D[{r Cos[\[Theta]], r Sin[\[Theta]],  ...

- asked by Matthew Leingang (85 votes), answered by Heike (74 votes)

—————————-

[How to create a new ”person curve”?] http://mathematica.stackexchange.com/questions/17704/how-to-create-a-new-person-curve

Wolfram—Alpha has a whole collection¹ of parametric curves that create images of famous people. To see them, enter WolframAlpha[”person curve”] into a Mathematica notebook, or person curve into ...

- asked by Simon (61 votes), answered by Vitaliy Kaurov (30 votes)

================================== Can you answer these? ==================================

[Unix-like reference to parent and root Association?] http://mathematica.stackexchange.com/questions/131337/unix-like-reference-to-parent-and-root-association

Is there a syntax or function to reference parent and root
when querying nested  Associations similar to Unix
".." and "/", eg "cd ../../mydir". ?

Here’s a typical application of the root ...

- asked by alancalvitti (3 votes)

—————————-

[Strange behaviour of FullSimplify when checking an equality of SparseArray’s] http://mathematica.stackexchange.com/questions/131400/strange-behaviour-of-fullsimplify-when-checking-an-equality-of-sparsearrays

I stumbled upon the following strange behaviour. Disclaimer: I present the simplest instance that I could find in which some behaviour occurs that I first noticed in a different, more complicated ...

- asked by Jules Lamers (1 vote)

—————————-

[ListPlot PlotRange Ignored with all Missing or empty data] http://mathematica.stackexchange.com/questions/131321/listplot-plotrange-ignored-with-all-missing-or-empty-data

I have a function that uses ListPlot to draw a custom plot. When a data value is not applicable I pass in Missing to prevent ListPlot and its Prolog option from displaying the point the function will ...

- asked by Edmund (3 votes)

44 Tuesday, November 15, 2016

==================================
Top new questions this week:
==================================

[Why (and when) does pattern matching with f[__] perform MUCH more quickly than _f?] http://mathematica.stackexchange.com/questions/130984/why-and-when-does-pattern-matching-with-f-perform-much-more-quickly-than

Consider this expression in Mathematica 10.3 (and above) on MacOS X:

expr = a b c d e f g h i j k l m n o p q r s t myG[u] myF[a, b]

Now compare the time it takes to apply the following ...

- asked by QuantumDot (22 votes), answered by WReach (17 votes)

—————————-

[Getting wrong limit with Bessel] http://mathematica.stackexchange.com/questions/130741/getting-wrong-limit-with-bessel

I computed a following limit (related to the asymptotic expansion of the sequence A000009 - number of partitions of n into distinct parts)

Expand[Limit[(((π BesselI[1, (Sqrt[1/24 + n]  ...

- asked by Vaclav Kotesovec (11 votes), answered by Akku14 (9 votes)

—————————-

[Join lists by observing x-value] http://mathematica.stackexchange.com/questions/130903/join-lists-by-observing-x-value

Hi everybody I have as a small test with two datasets (normally I have 100 datasets with 4100 brackets):

Dataset1={{20,1},{30, 1.3}, {40, 0.4}, {50, 0.9}}
Dataset2={{30, 1.2}, {40, 1}, {50, 0.4},  ...

- asked by Jacccy (10 votes), answered by ubpdqn (13 votes)

—————————-

[How to distribute Mathematica packages as paclets?] http://mathematica.stackexchange.com/questions/131101/how-to-distribute-mathematica-packages-as-paclets

Mathematica does have a nice package manager. Packages are called paclets, and they can be managed using the functions from the PacletManager‘ context.

How can I package up my own packages as ...

- asked by Szabolcs (9 votes), answered by Szabolcs (7 votes)

—————————-

[Does function call via @ ignore HoldFirst attribute?] http://mathematica.stackexchange.com/questions/130889/does-function-call-via-ignore-holdfirst-attribute

I was trying to test whether using func[x,y] is the same as func[#,y]&amp;@x:

SetAttributes[test, HoldFirst]
test[1 + 2 - 3, 5 - 5]
test[#, 5 - 5] &amp;@(1 + 2 - 3)

  test[1 + 2 - 3, 0]

...

- asked by Ruslan (8 votes), answered by m_goldberg (9 votes)

—————————-

[Graph visualization: Leave gap between vertex and endpoint of edge] http://mathematica.stackexchange.com/questions/130821/graph-visualization-leave-gap-between-vertex-and-endpoint-of-edge

This is a nice graph:

g = CycleGraph[4];

Graph[g, VertexCoordinates -&gt; {{0, 0}, {0, 1}, {1, 1}, {1, 0}},
 VertexLabels -&gt; Placed["Name", Center], VertexSize -&gt; Medium,
 EdgeShapeFunction  ...

- asked by cyrille.piatecki (8 votes), answered by kglr (12 votes)

—————————-

[Help finding the centre of a faint, incomplete circle?] http://mathematica.stackexchange.com/questions/130787/help-finding-the-centre-of-a-faint-incomplete-circle

so I found a program in the answers to this question that I thought was brilliant, so here it is applied to my situation: I have the image

and here’s the code:

...

- asked by Mason (8 votes)

================================== Greatest hits from previous weeks: ==================================

[How can Mathematica be used to create images like these?] http://mathematica.stackexchange.com/questions/118992/how-can-mathematica-be-used-to-create-images-like-these

Here are two examples of artistic image interpolation using just black lines:

TRIANGULATION: ANGULAR CELEBRITIES DRAWN WITH A PEN Interpolation for Triangulation-represented Digital Image

The ...

- asked by R Hall (28 votes), answered by MarcoB (29 votes)

—————————-

[How do you make a Neural Net?] http://mathematica.stackexchange.com/questions/123458/how-do-you-make-a-neural-net

In the new Mathematica release (v11), NeuralNetworks is one of the new main features. However, the documentation isn’t that clear on what function should be used in a Net.

The documentation on ...

- asked by JHM (22 votes), answered by Searke (24 votes)

================================== Can you answer these? ==================================

[Understanding the structure of an InterpolatingFunction] http://mathematica.stackexchange.com/questions/131063/understanding-the-structure-of-an-interpolatingfunction

FunctionInterpolation[x^2, {x, 0, 9}] // InputForm

returns:

InterpolatingFunction[ 0., 9., 5, 3, 0, 13, 4, 0, 0, 0, 0, Automatic, , , False, 0., 0.75, 1.5, 2.25, 3., 3.75, ...

- asked by anderstood (1 vote)

—————————-

[Is it possible to create .stp 3D model from Graphics3D?] http://mathematica.stackexchange.com/questions/130883/is-it-possible-to-create-stp-3d-model-from-graphics3d

I want to create some 3D solid model by Mathematica, and then export it into stp (step) format for further finite element or finite volume analysis in Fluent/ANSYS or Abaqus.

But so far to me, it ...

- asked by user6043040 (3 votes)

—————————-

[Time constrained loop unit] http://mathematica.stackexchange.com/questions/131159/time-constrained-loop-unit

I have a particularly difficult loop, in that it consists of two variables looping and sowing the result if a criteria is met. Overall it works for me, but some certain values for my variables take ...

- asked by Castle (2 votes)

45 Tuesday, November 8, 2016

==================================
Top new questions this week:
==================================

[For a better animation of the solution from NDSolve] http://mathematica.stackexchange.com/questions/130502/for-a-better-animation-of-the-solution-from-ndsolve

I obtained a numerical solution from the following code with NDSolve

L = 20;
tmax = 27;
\[Sigma] = 2;
myfun = First[h /. NDSolve[{D[h[x, y, t], t] +
Div[h[x, y, t]^3*Grad[Laplacian[h[x, y, t], {x,  ...

- asked by jsxs (12 votes), answered by Nasser (14 votes)

—————————-

[A puzzling result of ”FullSimplify”] http://mathematica.stackexchange.com/questions/130606/a-puzzling-result-of-fullsimplify

When I input:

FullSimplify[(1 - a^2)/b^2, a^2 + b^2 == 1]

the result is the ideal answer 1;

However,if I input:

FullSimplify[(1 - b^2)/a^2, a^2 + b^2 == 1]


the result is (1 - b^2)/a^2  ...

- asked by dabuyang (11 votes), answered by Bob Hanlon (7 votes)

—————————-

[ImageFeatureTrack or ImageDisplacements to measure average object velocities in images] http://mathematica.stackexchange.com/questions/130391/imagefeaturetrack-or-imagedisplacements-to-measure-average-object-velocities-in

I have as example a set of 30 gray scale images (8bit, 568*478 pixels, they are avalable here: http://tinyurl.com/zckyv9w where bright objects on dark background move from image to image mainly ...

- asked by mrz (9 votes), answered by Simon Woods (10 votes)

—————————-

[Documentation Tools: Don’t put web URL in user package docs] http://mathematica.stackexchange.com/questions/130515/documentation-tools-dont-put-web-url-in-user-package-docs

I am exploring the Workbench documentation tools for the first time and one of the difficulties I encountered was that every generated (compiled) documentation page includes weblinks. These point to ...

- asked by Szabolcs (9 votes)

—————————-

[How to make plots ’blacker’?] http://mathematica.stackexchange.com/questions/130471/how-to-make-plots-blacker

I need to make a contour plot for publication, but even if I
set ContourStyle-&gt;Black, the black plots and the axes are very faint.
When I export the figure in svg and open it in some  ...

- asked by Physicist (9 votes), answered by Michael E2 (10 votes)

—————————-

[How to specify algebraic relations between objects?] http://mathematica.stackexchange.com/questions/130258/how-to-specify-algebraic-relations-between-objects

so I’m wanting to screw around a bit with Geometric Algebra in Mathematica. To start, I want to create some basis objects: e1, e2, e3   and then specify the relations between them which are

- asked by Mason (9 votes), answered by march (9 votes)

—————————-

[Crack it If you Can? BUT in the BEST way] http://mathematica.stackexchange.com/questions/130566/crack-it-if-you-can-but-in-the-best-way

From the Wolfram Community:

Hello everyone,

A little while ago I was asked to solve this ”safe cracker” puzzle, a sweet example of a coffee table puzzle. The basic gist of this puzzle is that it ...

- asked by Youphyso (8 votes), answered by george2079 (4 votes)

================================== Greatest hits from previous weeks: ==================================

[Writing a word with straight lines] http://mathematica.stackexchange.com/questions/113403/writing-a-word-with-straight-lines

Here is an interesting way to write a word: (it is from a poster for the International Museum Day 2006; I believe it even won an award at an international design competition)

by Boris Ljubicic. ...

- asked by VividD (72 votes), answered by Anton Antonov (34 votes)

—————————-

[Where can I find examples of good Mathematica programming practice?] http://mathematica.stackexchange.com/questions/18/where-can-i-find-examples-of-good-mathematica-programming-practice

I consider myself a pretty good Mathematica programmer, but I’m always looking out for ways to either improve my way of doing things in Mathematica, or to see if there’s something nifty that I haven’t ...

- asked by J. M. (441 votes), answered by faysou (396 votes)

================================== Can you answer these? ==================================

[Passing boolean parameters to a .NET Method using NETLink] http://mathematica.stackexchange.com/questions/130658/passing-boolean-parameters-to-a-net-method-using-netlink

According to the NETLink documentation, NETLink automatically handles type conversions from Mathematica to a .NET dll. One of the issues I have is that the .NET method I want to use expects a Boolean ...

- asked by user39464 (1 vote)

—————————-

[ParametricPlot3D Self Intersection] http://mathematica.stackexchange.com/questions/130460/parametricplot3d-self-intersection

I would like to know where my ParametricPlot3D intersects itself and to extract all intersections (points, lines, surfaces...) to animate them by changing P:

ParametricPlot3D[{fX[u,v,P], fY[u,v,P],  ...

- asked by chkone (3 votes)

—————————-

[Faster solution to combinatorial problem of two-part contractions] http://mathematica.stackexchange.com/questions/130598/faster-solution-to-combinatorial-problem-of-two-part-contractions

Given a list of elements I need all possible pairings of elements with a leading factor that describes the number of permutations. A (ugly but) working version would be:

list = {a, b, c, d};
 res =  ...

- asked by pbx (2 votes)

46 Tuesday, November 1, 2016

==================================
Top new questions this week:
==================================

[Huge bug involving MultinormalDistribution?] http://mathematica.stackexchange.com/questions/129916/huge-bug-involving-multinormaldistribution

Bug introduced in 8.0 or earlier and persisting through 11.0.1

I found a strange behavior regarding the CDF of the bivariate Normal distribution

...

- asked by fwgb (21 votes), answered by Eric Towers (19 votes)

—————————-

[GeoDistance - higher spatial resolution / precision?] http://mathematica.stackexchange.com/questions/130044/geodistance-higher-spatial-resolution-precision

I’m having a small problem with GeoDistance.

I’ve chosen a target city – San Francisco – and I’ve computed distances from SF to five other cities. Then I draw circles around each city, with radius ...

- asked by ConvexMartian (9 votes), answered by jose (4 votes)

—————————-

[How to extract the first dimension in TimeSeries?] http://mathematica.stackexchange.com/questions/129836/how-to-extract-the-first-dimension-in-timeseries

I want to extract the first dimension in TimeSeries,for example:

So I use this code:

data = Normal@AudioLocalMeasurements[ExampleData[{"Audio", "PianoScale"}],"MFCC"];
Thread[{data[[All, 1]],  ...

- asked by partida (9 votes), answered by kglr (6 votes)

—————————-

[How to recover Pauli matrices properties in Mathematica?] http://mathematica.stackexchange.com/questions/129799/how-to-recover-pauli-matrices-properties-in-mathematica

I want to do a cross or dot product involving a vector of Pauli matrices σ=(σ1,σ2,σ3); for example, σxσ=2iσ or σ.σ=3I.

Is there a simple way to do these operations?

- asked by user3654016 (8 votes), answered by corey979 (10 votes)

—————————-

[Flatten sublists within a bigger list] http://mathematica.stackexchange.com/questions/130011/flatten-sublists-within-a-bigger-list

Really sorry if this question is a duplicate. I couldn’t find exactly what I was looking for.

Here is a list I have:

{{{0. + 0.1875 I, 0. + 0.105469 I, 0. + 0.03125 I, 0. + 0.00390625 I,
   0. +  ...

- asked by jrekier (7 votes), answered by Edmund (6 votes)

—————————-

[7-dimensional cross product] http://mathematica.stackexchange.com/questions/129863/7-dimensional-cross-product

How to define a 7-dimensional cross product?

$$\begin{aligned}\mathbf {x} \times \mathbf {y} =(x_{2}y_{4}-x_{4}y_{2}+x_{3}y_{7}-x_{7}y_{3}+x_{5}y_{6}-x_{6}y_{5})\,&amp;\mathbf {e}  ...

- asked by corey979 (7 votes), answered by Sumit (4 votes)

—————————-

[How to draw a clock-diagram?] http://mathematica.stackexchange.com/questions/129960/how-to-draw-a-clock-diagram

I found a clock-diagram in a paper, so I would like to draw it in Mathematica. The main trouble for me is the corresponding line segments on the circle.

I would let the data1 lie the outside on the ...

- asked by user123 (7 votes), answered by Feyre (7 votes)

================================== Greatest hits from previous weeks: ==================================

[How can Mathematica be used to create images like these?] http://mathematica.stackexchange.com/questions/118992/how-can-mathematica-be-used-to-create-images-like-these

Here are two examples of artistic image interpolation using just black lines:

TRIANGULATION: ANGULAR CELEBRITIES DRAWN WITH A PEN Interpolation for Triangulation-represented Digital Image

The ...

- asked by R Hall (28 votes), answered by MarcoB (29 votes)

—————————-

[How to tell Mathematica that certain variables are real/imaginary, integer-valued, etc] http://mathematica.stackexchange.com/questions/66273/how-to-tell-mathematica-that-certain-variables-are-real-imaginary-integer-value

I’m trying to expedite some quantum mechanical calculations by running them through Mathematica. Expectation values and stuff like that. When I say, for example,

u[x_] := Sqrt[2/L] * Sin[Pi * n * x /  ...

- asked by Matthew Brunetti (8 votes), answered by SquareOne (6 votes)

================================== Can you answer these? ==================================

[How to Inset a legend in GeoGraphics with Scaled LegendMarkerSize?] http://mathematica.stackexchange.com/questions/130060/how-to-inset-a-legend-in-geographics-with-scaled-legendmarkersize

I have a GeoGraphics where I am using Scaled in PointSize to include size information. I want to Inset a PointLegend that describes the sizes of the points.

Outside of GeoGraphics I can do this by ...

- asked by Edmund (2 votes)

—————————-

[NumberLinePlot with Exponential] http://mathematica.stackexchange.com/questions/129938/numberlineplot-with-exponential

I have:

Clear[f, x]
f[x_] = Exp[1/x]


Now, the question is "where is the derivative negative?" I
managed to get the Reduce command to work by adding Reals.

Reduce[f[x] &lt; 0, x, Reals]

Which ...

- asked by David (3 votes)

—————————-

[Detect numbers on the image] http://mathematica.stackexchange.com/questions/129821/detect-numbers-on-the-image

How to detect numbers on the following image

I tried:

  img=Import["http://imgur.com/TDbn7sB.png"]

  set = ImagePartition[img, Scaled[{1/20, 1/5}]] // Flatten

then I tried Classify[] but it ...

- asked by vito (3 votes)

47 Tuesday, October 25, 2016

==================================
Top new questions this week:
==================================

[How to improve this plot?] http://mathematica.stackexchange.com/questions/129426/how-to-improve-this-plot

In general, the quality of Mathematica graphics is beyond praise. However, the output of Plot3D command is somewhat unexpected in the following code. Let’s solve the Dirichlet problem for the ...

- asked by user64494 (11 votes), answered by Simon Woods (16 votes)

—————————-

[Neural Networks: Does Mathematica (v11) experimental code support state-of-art Models?] http://mathematica.stackexchange.com/questions/129469/neural-networks-does-mathematica-v11-experimental-code-support-state-of-art-m

Mathematica made a big step implementing Neural Networks. I checked some examples for deep learning (ChainNet), also the related link. I see that model structures such as LaNet can be developed. ...

- asked by s.s.o (10 votes), answered by Alexey Golyshev (8 votes)

—————————-

[Converting Game of Life images to lists] http://mathematica.stackexchange.com/questions/129135/converting-game-of-life-images-to-lists

I want to convert images of GoL configurations into binary matrices to run in Mathematica’s CellularAutomaton. I know that there’s a collection of GoL patterns in http://conwaylife.com and other ...

- asked by andandandand (10 votes), answered by C. E. (5 votes)

—————————-

[JDBC-to-ODBC bridge gone. How to connect to SQL Server now in case of Windows Authentication?] http://mathematica.stackexchange.com/questions/129160/jdbc-to-odbc-bridge-gone-how-to-connect-to-sql-server-now-in-case-of-windows-au

Connecting to our corporate SQL servers using JDBC never worked for me, perhaps related to the Windows Authentication method that is necessary in our network. However, I found out that configuring the ...

- asked by Sjoerd C. de Vries (8 votes), answered by Sjoerd C. de Vries (6 votes)

—————————-

[How to speed up calculations on big symbolic matrices?] http://mathematica.stackexchange.com/questions/129465/how-to-speed-up-calculations-on-big-symbolic-matrices

this is my first time posting something on a community of the StackExchange platform, so please feel free to correct me if I’m doing something wrong. :) Additionally you should probably know that I’m ...

- asked by TSwift (8 votes)

—————————-

[How do I ’Join’ two Structured Datasets?] http://mathematica.stackexchange.com/questions/129116/how-do-i-join-two-structured-datasets

Consider the following Datasets

dsCompetitions with fields ”id”,”name”,”eventTypeId”

dsEventTypes with fields ”id”, ”name”

I want to join the datasets as follows using SQL pseudocode:

SELECT ...

- asked by nilo de roock (8 votes), answered by rcollyer (7 votes)

—————————-

[Why isn’t Orderless an Attribute of And?] http://mathematica.stackexchange.com/questions/129415/why-isnt-orderless-an-attribute-of-and

In standard logic And is a commutative operator. Still, in Mathematica, And doesn’t have the Orderless attribute:

Attributes[And]
(* {Flat,HoldAll,OneIdentity,Protected} *)

This may have not been ...

- asked by Soldalma (7 votes), answered by JHM (6 votes)

================================== Greatest hits from previous weeks: ==================================

[Programming the fiver game] http://mathematica.stackexchange.com/questions/120959/programming-the-fiver-game

Obviously, even if I ask a lot of question I am, obviously, still a dummy!!!!

I want to program the fiver game. It’s a very simple game played solitary on a 5× 5  the rule is elementary : if ...

- asked by cyrille.piatecki (12 votes), answered by Mr.Wizard (19 votes)

—————————-

[How to make an inkblot?] http://mathematica.stackexchange.com/questions/3345/how-to-make-an-inkblot

How to effectively create a polygon that looks like a realistic inkblot? So far, I could come up with this (borrowing from Ed Pegg Jr.’s Rorschach demonstration):

RandomBlot[num_, opts___] :=  ...

- asked by István Zachar (83 votes), answered by Sjoerd C. de Vries (46 votes)

================================== Can you answer these? ==================================

[Counting the occurences of entries in a dataset columnwise] http://mathematica.stackexchange.com/questions/129459/counting-the-occurences-of-entries-in-a-dataset-columnwise

Consider a dataset with some rows and considerably less columns (eg something like 10x3). Assume that the contents of the dataset cells are integers from some conveniently chosen range (eg 1 through ...

- asked by user42582 (1 vote)

—————————-

[List, Association, and Dataset, according to what principles to choose which one to use?] http://mathematica.stackexchange.com/questions/129081/list-association-and-dataset-according-to-what-principles-to-choose-which-one

List, Association and Dataset are three ’objects’ that can be used to store data in MMA. So when or under what conditions for one to decide to use each of them?

- asked by Alexander Zeng (2 votes)

—————————-

[How to ArrayFlatten some matrix which have repeated element] http://mathematica.stackexchange.com/questions/129153/how-to-arrayflatten-some-matrix-which-have-repeated-element

I have many such matrices(whose dimension are all 3*3.) like:

list1={{0,3,0},{4,1,2},{0,5,0}};
list2={{0,6,0},{1,2,8},{0,7,0}};
list3={{0,1,0},{9,5,7},{0,11,0}};
list4={{0,2,0},{5,7,10},{0,12,0}};

...

- asked by yode (3 votes)

48 Tuesday, October 18, 2016

==================================
Top new questions this week:
==================================

[Why removing a function and defining it on the same line does not work?] http://mathematica.stackexchange.com/questions/128818/why-removing-a-function-and-defining-it-on-the-same-line-does-not-work

Why do the two pieces of code below yield rather different results? The only difference is that in the first one the function definition is in the same line as the Remove command while in the second ...

- asked by Fernando Saldanha (17 votes), answered by dan7geo (16 votes)

—————————-

[House of Santa Claus] http://mathematica.stackexchange.com/questions/128741/house-of-santa-claus

The house of Santa Claus is an old German drawing game for small children. You have to draw a house in one line. You must not lift your pencil while drawing.

 $\color{red}{\text{You must not repeat a  ...

- asked by mrz (15 votes), answered by Dr. Wolfgang Hintze (9 votes)

—————————-

[how to get cell boundaries in the image] http://mathematica.stackexchange.com/questions/128596/how-to-get-cell-boundaries-in-the-image

I have a microscope image of some animal tissue and wish to get the contours for all the cells that are present in the image. the cells are connected to the neighbouring cells via these contours. At ...

- asked by Ali Hashmi (10 votes), answered by corey979 (13 votes)

—————————-

[Numerically solve the initial value problem for the 1-D wave equation] http://mathematica.stackexchange.com/questions/128516/numerically-solve-the-initial-value-problem-for-the-1-d-wave-equation

I want to solve the standard 1-dimensional wave equation y  = y
 xx   tt  using NDSolve (for y(x,t)  ) with the following conditions:

cond1 = Piecewise[{{1 - Abs[x - 1], Abs[x - 1] &lt; 1}, {0, Abs[x  ...

- asked by arcbloom (8 votes), answered by xzczd (7 votes)

—————————-

[Dataset Processing: efficient ways to clean and merge sets for Life Sciences] http://mathematica.stackexchange.com/questions/128519/dataset-processing-efficient-ways-to-clean-and-merge-sets-for-life-sciences

Dataset Processing (for Life Sciences)

Note: a related, but distinct task is posted here ID Swapping: Efficient use of a reference table to convert ID values.

A common task, at least for me, ...

- asked by SumNeuron (8 votes), answered by SumNeuron (5 votes)

—————————-

[Rotations of a number] http://mathematica.stackexchange.com/questions/128666/rotations-of-a-number

If we start with a number like 1234 and produce the following sum 1234 + 123 + 12 + 1 = 1370.

If we are given the 1370 can I retrieve the 1234? A similar question was migrated over to the Math.SE ...

- asked by bobbym (8 votes), answered by J. M. (6 votes)

—————————-

[What’s wrong with the Sum function?] http://mathematica.stackexchange.com/questions/128534/whats-wrong-with-the-sum-function

Here are the codes:

f[n_]:=Sum[1,{K,0,n},{M,0,n-K},{La,0,K},{Lb,0,n-K-M},{Lc,0,M}]//Simplify

g[n_]:=Sum[1,{La,0,n},{Lb,0,n-La},{Lc,0,n-La-Lb},{K,La,n-Lb},{M,Lc,n-K-Lb}]//Simplify

f[x]/.x-&gt;5

...

- asked by lamberto (7 votes), answered by Bob Hanlon (3 votes)

================================== Greatest hits from previous weeks: ==================================

[Creating legends for plots with multiple lines?] http://mathematica.stackexchange.com/questions/4025/creating-legends-for-plots-with-multiple-lines

So I have a graph with multiple lists, for e.g.

data = {{1,2}, {3,4}, {3,5}, {2,3} . . .}


If I then do ListLinePlot[Table[{#1,Log[b,#2]}&amp;@@@data, {b,1,10,2}]] I have
no way to generate a legend  ...

- asked by Eiyrioü von Kauyf (59 votes), answered by Jens (88 votes)

—————————-

[Exporting graphics to PDF - huge file] http://mathematica.stackexchange.com/questions/1542/exporting-graphics-to-pdf-huge-file

I want to draw some basic surfaces, export them to PDF and include them in a LaTeX file. I create a simple 3D graphics object, for instance with

 ParametricPlot3D[{r Cos[\[Theta]], r Sin[\[Theta]],  ...

- asked by Matthew Leingang (85 votes), answered by Heike (74 votes)

================================== Can you answer these? ==================================

[Parallelizing code, any tips?] http://mathematica.stackexchange.com/questions/128905/parallelizing-code-any-tips

I have access to a Linux cluster and I’m trying to use Parallelize to run the above bellow faster, but whenever I try to place Parallelize in any other parts, besides the loop, where I think it may ...

- asked by Sergio Parreiras (2 votes)

—————————-

[Does Reduce have problems with greek symbols that lead to wrong results?] http://mathematica.stackexchange.com/questions/128965/does-reduce-have-problems-with-greek-symbols-that-lead-to-wrong-results

I call Reduce on the following simple system of inequalities

e = ((-4 + Sqrt[(-2 + λ)^2] + 3 λ) Log[p] + 4 λ Log[β])/(2 λ);
Reduce[e &gt; 0 &amp;&amp; 1 &gt; λ &gt; 0 &amp;&amp; 1 &gt; p &gt; 0  ...

- asked by klm (3 votes)

—————————-

[Full screen image in slideshow?] http://mathematica.stackexchange.com/questions/128875/full-screen-image-in-slideshow

Is it possible to make an image fill up and entire slide in a slideshow notebook so that there are no cell brackets or any white space around it at all (when viewed in presentation mode of course)?

- asked by M.R. (1 vote)

49 Tuesday, October 11, 2016

==================================
Top new questions this week:
==================================

[How to programmatically play an Audio object?] http://mathematica.stackexchange.com/questions/128147/how-to-programmatically-play-an-audio-object

A Sound object can be programmatically played using EmitSound. Example:

snd = ExampleData[{"Sound", "AltoFlute"}];

Button["Play!", EmitSound[snd]]

What about an Audio object?

- asked by Szabolcs (14 votes), answered by Szabolcs (9 votes)

—————————-

[TreePlot does not give a ”binary-looking” tree for a binary tree] http://mathematica.stackexchange.com/questions/128323/treeplot-does-not-give-a-binary-looking-tree-for-a-binary-tree

I use the following code to generate a binary tree with root 1.

TreePlot[{1 -&gt; 2, 1 -&gt; 3, 2 -&gt; 4, 2 -&gt; 5, 3 -&gt; 6, 3 -&gt; 7, 4 -&gt; 8,
  4 -&gt; 9, 5 -&gt; 10, 5 -&gt; 11, 6 -&gt;  ...

- asked by Tony (13 votes), answered by WReach (19 votes)

—————————-

[Partition array without unpacking] http://mathematica.stackexchange.com/questions/128133/partition-array-without-unpacking

What is the simplest way to partition a list into equal-length sublists, allow the last sublist to be shorter of necessary, and avoid unpacking?

Partition doesn’t usually unpack:

arr = RandomReal[1,  ...

- asked by Szabolcs (13 votes), answered by Szabolcs (7 votes)

—————————-

[Creating a simple Dock Cell that Fades In when Cursor Hover Over It] http://mathematica.stackexchange.com/questions/128025/creating-a-simple-dock-cell-that-fades-in-when-cursor-hover-over-it

I like to create dock cells, that enhance the look of my notebooks. Do you know of a simple way to get the functionality in iBooks shown below in the video. I want the dock cell in Mathematica to ...

- asked by Michael McCain (13 votes), answered by Karsten 7. (14 votes)

—————————-

[Why are Exp[3] and 2 treated differently within Complex?] http://mathematica.stackexchange.com/questions/128211/why-are-exp3-and-2-treated-differently-within-complex

Why doesn’t the last command below split the complex number into its real and imaginary parts?

Complex[2,2]
(* 2 + 2 I *)
Complex[N[Exp[3]], N[Exp[3]]]
(* 20.0855 + 20.0855 I *)
 ...

- asked by Fernando Saldanha (12 votes), answered by Szabolcs (18 votes)

—————————-

[KeyDrop does not respect Key in V11] http://mathematica.stackexchange.com/questions/128171/keydrop-does-not-respect-key-in-v11

KeyDrop[&lt;|a -&gt; 1|&gt;, Key[a]]

&lt;|a -&gt; 1|&gt;

KeyTake[&lt;|a -&gt; 1|&gt;, Key[a]]

&lt;||&gt;

closely related but not the same: Unexpected behavior of KeyTake

Are there any ...

- asked by Kuba (11 votes), answered by Xavier (5 votes)

—————————-

[Strategies for creating 3D text] http://mathematica.stackexchange.com/questions/128412/strategies-for-creating-3d-text

I am interested in using Mathematica to create 3D text for printing. I stumbled upon this answer which works very well in a slightly modified form:

text3D[text_String, mult_] := ListPlot3D[
   ...

- asked by bobthechemist (10 votes), answered by J. M. (14 votes)

================================== Greatest hits from previous weeks: ==================================

[Is it possible to export the equations from Mathematica to MATLAB?] http://mathematica.stackexchange.com/questions/14035/is-it-possible-to-export-the-equations-from-mathematica-to-matlab

Is it possible to export the output expressions from Mathematica computations (e.g., equations) in valid MATLAB syntax?

- asked by Seyhmus Güngören (24 votes), answered by R. M. (32 votes)

—————————-

[Labeling individual curves in Mathematica] http://mathematica.stackexchange.com/questions/4444/labeling-individual-curves-in-mathematica

I need to create a plot for export and inclusion in a report. Is there a better way to label curves than PlotLegends? From what I’ve read and my personal experience, PlotLegends is pretty bad.

Is ...

- asked by Tianxiang Xiong (47 votes), answered by Artes (37 votes)

================================== Can you answer these? ==================================

[Help: Reclassify] http://mathematica.stackexchange.com/questions/128194/help-reclassify

Is it possible to improve the current ClassifierFunction with more training data without running the previous training again?

In this way i will be able to deal with very large datasets in chunks.

- asked by user13892 (5 votes)

—————————-

[Pattern matching problem in version 11.01] http://mathematica.stackexchange.com/questions/128247/pattern-matching-problem-in-version-11-01

Consider this simple example:

p1 = ListPlot3D[
   Table[Sin[j^2 + i], {i, 0, Pi, Pi/5}, {j, 0, Pi, Pi/5}],
   Mesh -&gt; None, Axes -&gt; False, Boxed -&gt; False, ColorFunction -&gt; Hue];
p2 =  ...

- asked by xslittlegrass (8 votes)

—————————-

[CUDADot runs slowly and writes ”CUDALink experienced a kernel launch failure” with matrix size ¿ 3300] http://mathematica.stackexchange.com/questions/128124/cudadot-runs-slowly-and-writes-cudalink-experienced-a-kernel-launch-failure-wi

I am trying to learn CUDA and start from the help examples.
It turnes out that CPU calculation is much faster for
matrix sizes &lt; 3200 than CUDA, while CUDADot gives the error for sizes > 3300. I  ...

- asked by luu (4 votes)

50 Tuesday, October 4, 2016

==================================
Top new questions this week:
==================================

[UIperformance with large image data] http://mathematica.stackexchange.com/questions/127523/ui-performance-with-large-image-data

Some days ago, I built a small program for some of my colleagues to analyse cell images. One minor part of the user interface was the selection of the region of interest. The images are large and need ...

- asked by halirutan (25 votes), answered by Kuba (21 votes)

—————————-

[Transform sphere to an ellipse in R2   ] http://mathematica.stackexchange.com/questions/127645/transform-sphere-to-an-ellipse-in-r2

In Lay’s Linear Algebra and Its Applications textbook, he defines the matrix

    [                    ]
A =  4  amp; 11   amp;14
     8   amp; 7  amp; − 2
and claims that the transformation T(x) = Ax  ...

- asked by David (15 votes), answered by yarchik (17 votes)

—————————-

[Did Fibonacci slow down?] http://mathematica.stackexchange.com/questions/127876/did-fibonacci-slow-down

For Fibonacci numbers we have a nice formula:

(    √ -)n  (    √ -)n
-1-+---5--−√-1-−---5--
        2n  5

We can implement that in Mathematica:

a[n_]:=  ...

- asked by Fred Simons (13 votes), answered by Szabolcs (20 votes)

—————————-

[I would like to create a fractal by copying, scaling and rotating the initial element] http://mathematica.stackexchange.com/questions/127458/i-would-like-to-create-a-fractal-by-copying-scaling-and-rotating-the-initial-el

I want to create a fractal, which looks like this:

This is rule 150R, which can be found in NKS, page 439.

However, instead of using a cellular automaton, I want to create this fractal from a ...

- asked by Yuriy S (13 votes), answered by wxffles (13 votes)

—————————-

[Mathematica + Pythonika on the Raspberry pi] http://mathematica.stackexchange.com/questions/127802/mathematica-pythonika-on-the-raspberry-pi

Due to the high availability of python code for the rpi, I’m trying to call python functions from Mathematica. I know that pythonika works well on OS X, but I can’t compile it on the Raspberry pi.

...

- asked by elbOlita (12 votes), answered by elbOlita (13 votes)

—————————-

[How to map and sum a list fast?] http://mathematica.stackexchange.com/questions/127658/how-to-map-and-sum-a-list-fast

The following takes a lot of memory and is slow:

Timing[Total[Map[#^2 &amp;, Range[1, 100000000]]]]

I suspect this is because it first calculates and stores the whole list of squared numbers and ...

- asked by Yrogirg (12 votes), answered by BlacKow (19 votes)

—————————-

[Implementing the Biham–Middleton–Levine traffic model as CellularAutomaton] http://mathematica.stackexchange.com/questions/127821/implementing-the-biham-middleton-levine-traffic-model-as-cellularautomaton

In an attempt to understand how to make rules for CellularAutomaton[], I set out to try to implement the Biham–Middleton–Levine traffic model.

It is a 2D, k=3 model with a 3x3 neighborhood, so the ...

- asked by HJensen (10 votes), answered by C. E. (5 votes)

================================== Greatest hits from previous weeks: ==================================

[What are the most common pitfalls awaiting new users?] http://mathematica.stackexchange.com/questions/18393/what-are-the-most-common-pitfalls-awaiting-new-users

As you may already know, Mathematica is a wonderful piece of software. However, it has a few characteristics that tend to confuse new (and sometimes not-so-new) users. That can be clearly seen from ...

- asked by Dr. belisarius (341 votes), answered by Michael E2 (197 votes)

—————————-

[How to make this beautiful animation] http://mathematica.stackexchange.com/questions/112700/how-to-make-this-beautiful-animation

How to make an animation of following gif in Mathematica?

Edit: The animation shown above was created by Charlie Deck in processing.

And how to make 3D analog?

I tried first few steps

line = ...

- asked by vito (47 votes), answered by C. E. (50 votes)

================================== Can you answer these? ==================================

[VectorPlot3D broken in Mathematica 11.0.1?] http://mathematica.stackexchange.com/questions/127724/vectorplot3d-broken-in-mathematica-11-0-1

Here is what I get when simply evaluating the example in the documentation:

This is on Win7 x64. I can see some vectors if I do something like

VectorPlot3D[{1, 1, 1}, {x, -1, 1}, {y, -1, 1}, {z,  ...

- asked by Pirx (5 votes)

—————————-

[Least squares approximation] http://mathematica.stackexchange.com/questions/127806/least-squares-approximation

I have data points which is mydata = 0, 0, 1, 1, 2, 0;

From this data, I need to do the least squares approximation by using Bernstein polynomials to produce a set of Bezier points. Before ...

- asked by NKamaru (2 votes)

—————————-

[Matching key-value pair without converting to List in KeyValueMap] http://mathematica.stackexchange.com/questions/127860/matching-key-value-pair-without-converting-to-list-in-keyvaluemap

I frequently use this method with KeyValueMap in order to match and refer to named parts (ie, ”myKey”, ”myValue”)

EDIT: to refer to named parts in the function f without an external function ...

- asked by alancalvitti (1 vote)

51 Tuesday, September 27, 2016

==================================
Top new questions this week:
==================================

[Should I always be using Module in functions unless I explicitly want global variables?] http://mathematica.stackexchange.com/questions/126877/should-i-always-be-using-module-in-functions-unless-i-explicitly-want-global-var

I define functions a ton. In the past, I’ve mostly just defined my functions like:

myFunc[var1_]:=(
  var2=var1^2;
  Return@var2;
)

And I haven’t run into too much trouble. If I wanted to be really ...

- asked by YungHummmma (15 votes), answered by WReach (18 votes)

—————————-

[Why this real integral yields imaginary results?] http://mathematica.stackexchange.com/questions/127301/why-this-real-integral-yields-imaginary-results

Integrate[(y - y^2 + x - x^2 + 2*x*y)/(1 - x - y),{x,0,1},{y, 0, 1}]

The above integral yields -1-4Iπ/3 in Mathematica. Since the integrand is real (although divergent at some points), how does ...

- asked by Chong Wang (12 votes), answered by bbgodfrey (12 votes)

—————————-

[Would it be a good idea to use Failure and FailureQ in own code] http://mathematica.stackexchange.com/questions/126908/would-it-be-a-good-idea-to-use-failure-and-failureq-in-own-code

Since version 10 (at least 10.0.2 but I think 10.0.0) there is Failure and since version 10.2 there is also FailureQ. As often the documentation is somewhat vague and says ”Failure is generated by ...

- asked by Albert Retey (12 votes), answered by Leonid Shifrin (9 votes)

—————————-

[Display grayscale image as 3d plot] http://mathematica.stackexchange.com/questions/127210/display-grayscale-image-as-3d-plot

How to build 3d plot of grayscale image where x,y - pixel coordinates, z - pixel intensity?

I tried ListPlot3D[ImageData[image]], but ImageData gives just intensities. I suppose a possible solution ...

- asked by red1ynx (10 votes), answered by Kuba (11 votes)

—————————-

[Automatically draw ellipsoids around groups of select points] http://mathematica.stackexchange.com/questions/126899/automatically-draw-ellipsoids-around-groups-of-select-points

Suppose you have a ListPlot, and there are certain points you wish to emphasize belong to particular group. I would like to make a function that automatically draws an ellipsoid around a select group ...

- asked by SumNeuron (10 votes), answered by Szabolcs (11 votes)

—————————-

[Enter colors directly into notebook?] http://mathematica.stackexchange.com/questions/127245/enter-colors-directly-into-notebook

In Mathematica notebook interface, you can evaluate:

In[1]:= Black

and you get a colored squared representing the color. Then I can copy and paste this color square and use it as input, like so:

...

- asked by becko (9 votes), answered by WReach (10 votes)

—————————-

[Large Dataset query fails if column contains Missing] http://mathematica.stackexchange.com/questions/126851/large-dataset-query-fails-if-column-contains-missing

In version 11.0 (Win 8.1 Pro) a query on a large Dataset for a column that contains Missing fails most unceremoniously.

With

dsTest = AssociationThread[{"a", "b"},
     If[Last@# == 10000,  ...

- asked by Edmund (9 votes), answered by JasonB (7 votes)

================================== Greatest hits from previous weeks: ==================================

[Is there an open source implementation of Mathematica-the-language?] http://mathematica.stackexchange.com/questions/4454/is-there-an-open-source-implementation-of-mathematica-the-language

I’ve seen questions before such as ”What is the best open-source equivalent for Mathematica?”, but that specific question (and that line of inquiry in general) cares more about the computer algebra ...

- asked by sblom (81 votes), answered by Simon (63 votes)

—————————-

[What are the most common pitfalls awaiting new users?] http://mathematica.stackexchange.com/questions/18393/what-are-the-most-common-pitfalls-awaiting-new-users

As you may already know, Mathematica is a wonderful piece of software. However, it has a few characteristics that tend to confuse new (and sometimes not-so-new) users. That can be clearly seen from ...

- asked by Dr. belisarius (341 votes), answered by Michael E2 (195 votes)

================================== Can you answer these? ==================================

[Enable file completion by default?] http://mathematica.stackexchange.com/questions/127203/enable-file-completion-by-default

File completions work for Import and Get but not with &lt;&lt; syntax as you can see:

Is there some way to enable this?

- asked by M.R. (2 votes)

—————————-

[Trouble with NIntegrate strategy ”DoubleExponentialOscillatory” when trying to ListPlot the results] http://mathematica.stackexchange.com/questions/126832/trouble-with-nintegrate-strategy-doubleexponentialoscillatory-when-trying-to-l

Can someone point me in the right direction? I ’ve been puzzling with this for weeks...

I have a huge function (of the form f(y,ξ)sin(ξx) ) to integrate in ξ in region (0, Infinity) and I use ...

- asked by George13 (1 vote)

—————————-

[Using an umlaut for a keyboard shortcut] http://mathematica.stackexchange.com/questions/126909/using-an-umlaut-for-a-keyboard-shortcut

How can I define a keyboard shortcut based on an umlaut like ü?

KeyEvent in KeyEventTranslations.tr doesn’t seem to register umlaut based keyboard inputs. For example, after adding

...

- asked by Karsten 7. (3 votes)

52 Tuesday, September 20, 2016

==================================
Top new questions this week:
==================================

[The paradigm behind Dynamic and related functionality] http://mathematica.stackexchange.com/questions/126471/the-paradigm-behind-dynamic-and-related-functionality

Dynamic and the related functionality strikes me as a very unique way to build quick and dirty personal GUIs which are great for experimentation.

I suspect that this is only because of my lack of ...

- asked by Szabolcs (24 votes), answered by Leonid Shifrin (21 votes)

—————————-

[Bug with iterated With: Referring to function arguments invalidates previous definitions] http://mathematica.stackexchange.com/questions/126425/bug-with-iterated-with-referring-to-function-arguments-invalidates-previous-def

G[x_] := With[{a = 0}, With[{b = x}, a]]
G @ 0
F[x_] := With[{a = 0}, {b = x}, a]
F @ 0

gives

  0
  a

I would expect both to behave exactly the same.

It seems that referring to the parameter ...

- asked by masterxilo (20 votes), answered by Kuba (20 votes)

—————————-

[How to quickly find all grid cells covered by a geometric region?] http://mathematica.stackexchange.com/questions/126346/how-to-quickly-find-all-grid-cells-covered-by-a-geometric-region

I’m trying to compute a complete set of unit grid cells (”pixels”) which a geometric region covers at least partially. I have constructed a method that produces correct results:

With[{reg =  ...

- asked by kirma (14 votes), answered by george2079 (9 votes)

—————————-

[Cone Trees: map a graph onto geometric shape] http://mathematica.stackexchange.com/questions/126657/cone-trees-map-a-graph-onto-geometric-shape

Question

Is it possible to map a Graph onto a geometric object such as a Cone?

Motivation

Visualizing large trees can be tedious, especially when limited to the confines of the printed page. One ...

- asked by SumNeuron (13 votes), answered by Szabolcs (18 votes)

—————————-

[Evaluate expressions within Vim] http://mathematica.stackexchange.com/questions/126449/evaluate-expressions-within-vim

I want to be able to type a quick Mathematica expression, such as

550/3. (e.g. common math),
Sum[i, {i, 0, n}]//TeXForm//ToString (e.g. writing LaTeX document), or
{55, 1, 10, 40, 9}//Total (e.g.  ...

- asked by Andrew MacFie (11 votes), answered by Andrew MacFie (11 votes)

—————————-

[Non newtonian calculus] http://mathematica.stackexchange.com/questions/126730/non-newtonian-calculus

I would like to define a new operator say

                   ( f[x+h]) 1h
stard[f[x]] = limh →0  -f[x]-

I think it must be done with an upvalue but I do not know how to ...

- asked by cyrille.piatecki (10 votes), answered by Szabolcs (18 votes)

—————————-

[How could I perform Region or Polygon Clipping in mathematica?] http://mathematica.stackexchange.com/questions/126463/how-could-i-perform-region-or-polygon-clipping-in-mathematica

I need to clip several regions reg: like Rectangle, Polygon, Ellipse... My goal isn’t to plot the clipping but to have a representation of each new region.

I searched if there was any package or ...

- asked by A.M. (10 votes), answered by george2079 (4 votes)

================================== Greatest hits from previous weeks: ==================================

[Beautiful dance of the Earth and Venus around the sun] http://mathematica.stackexchange.com/questions/115358/beautiful-dance-of-the-earth-and-venus-around-the-sun

I have seen very nice dynamic graphics created by users of Ma. I would like to get help whether the following graphics can be created using Ma. I was not able to create the dynamic picture here. ...

- asked by ramesh (12 votes), answered by ubpdqn (6 votes)

—————————-

[How can this image (optical illusion) be created with Mathematica?] http://mathematica.stackexchange.com/questions/24148/how-can-this-image-optical-illusion-be-created-with-mathematica

I came across this image the other day:

and liked the sensation of it pulsing. I was wondering if anyone would know how to create something similar with Mathematica (without the Pink Floyd Dark ...

- asked by Mike Honeychurch (53 votes), answered by halirutan (66 votes)

================================== Can you answer these? ==================================

[Smart Subscript] http://mathematica.stackexchange.com/questions/126736/smart-subscript

I have a question about subscript policy. For some reason I have some variables called Subscript[q, 1], Subscript[q, 2], Subscript[q, 3] and Subscript[q, 4]. I know that I could have called them in ...

- asked by MaPo (1 vote)

—————————-

[Difficult R installation] http://mathematica.stackexchange.com/questions/126501/difficult-r-installation

In RLink and R v3.0.1?, there is an update which say that the problem of the lack of compatibility between the expected version and the last version of R has been settled for version 10.0.1 of ...

- asked by cyrille.piatecki (2 votes)

—————————-

[Does Overflow[] poison session for N?] http://mathematica.stackexchange.com/questions/126337/does-overflow-poison-session-for-n

Summary: once Mathematica hits an overflow error, N[] appears to break for even simple calculations.

RealDigits[N[Sqrt[2]-1,10^8]];

I was impressed that Mathematica ran the code above (first 100 ...

- asked by barrycarter (9 votes)

53 Tuesday, September 13, 2016

==================================
Top new questions this week:
==================================

[Drawing picture with straight line (Petros Vrellis’s Art)] http://mathematica.stackexchange.com/questions/126161/drawing-picture-with-straight-line-petros-vrelliss-art

I am trying to extend Writing a word with straight lines for any picture/image. I guess the basic idea is to find a set of points in the image region and then draw random lines through them. Let’s ...

- asked by Sumit (16 votes), answered by Rahul (6 votes)

—————————-

[How do I count the most used functions across a set of notebooks?] http://mathematica.stackexchange.com/questions/125960/how-do-i-count-the-most-used-functions-across-a-set-of-notebooks

WolframLanguageData allows us to view the most used functions across several code bases like Wolfram Alpha, the documentation, or Stack Exchange. I was curious about the results for my own collection ...

- asked by Michael Hale (15 votes), answered by Michael Hale (11 votes)

—————————-

[How to ReplaceAll except within specified heads] http://mathematica.stackexchange.com/questions/125918/how-to-replaceall-except-within-specified-heads

ReplaceAll[expr, rule] and ReplaceRepeated[expr, rule] search through all subexpressions of expr applying rule where they match.

Are there built-in Mathematica functions that do the same thing, ...

- asked by QuantumDot (15 votes), answered by JHM (15 votes)

—————————-

[Is this a bug in Replace?] http://mathematica.stackexchange.com/questions/125771/is-this-a-bug-in-replace

Consider the following minimal examples. This one works as expected, replacing trees starting from the inside with a numerical value.

ClearAll[tree];
x = tree["A", {tree["B", {1, 2}], 3}];
Replace[x,  ...

- asked by István Zachar (14 votes), answered by Leonid Shifrin (17 votes)

—————————-

[How do I test if a variable represents a sequence?] http://mathematica.stackexchange.com/questions/126193/how-do-i-test-if-a-variable-represents-a-sequence

I created a variable that represents a sequence:

mySeq = Sequence[1, 2, 3];

I wanted to use that variable as an argument for some functions. But I got in trouble. For example,

FreeQ[mySeq, 1]

...

- asked by Fernando Saldanha (12 votes), answered by Edmund (8 votes)

—————————-

[How to calculate the numerical integral more efficiently?] http://mathematica.stackexchange.com/questions/126001/how-to-calculate-the-numerical-integral-more-efficiently

Rencently, I ecountered the following numerical intergral:

\begin{cases}
\mathbf I_1=\displaystyle \int_{t}\mathbf N {\mathbf N}^{\text T}{\rm d}t\\
\mathbf I_2=\displaystyle \int_{t}\mathbf N’’

- asked by Shutao Tang (11 votes), answered by Anton Antonov (8 votes)

—————————-

[Optional argument that can be completely omitted?] http://mathematica.stackexchange.com/questions/125929/optional-argument-that-can-be-completely-omitted

I am writing a simple function return similar words.

Clear[similarWords]
similarWords[string_]:=Nearest[WordList[],string]

I want to add another argument n which is optional. When it presents, it ...

- asked by matheorem (11 votes), answered by Szabolcs (12 votes)

================================== Greatest hits from previous weeks: ==================================

[Writing a word with straight lines] http://mathematica.stackexchange.com/questions/113403/writing-a-word-with-straight-lines

Here is an interesting way to write a word: (it is from a poster for the International Museum Day 2006; I believe it even won an award at an international design competition)

by Boris Ljubicic. ...

- asked by VividD (71 votes), answered by Anton Antonov (32 votes)

—————————-

[Exporting graphics to PDF - huge file] http://mathematica.stackexchange.com/questions/1542/exporting-graphics-to-pdf-huge-file

I want to draw some basic surfaces, export them to PDF and include them in a LaTeX file. I create a simple 3D graphics object, for instance with

 ParametricPlot3D[{r Cos[\[Theta]], r Sin[\[Theta]],  ...

- asked by Matthew Leingang (85 votes), answered by Heike (73 votes)

================================== Can you answer these? ==================================

[Finding covariation between datasets] http://mathematica.stackexchange.com/questions/125963/finding-covariation-between-datasets

For me this is a very fascinating problem, which I however lack the ability to deal with as well as the nomenclature to describe properly. (Please feel free to edit the title).

The conditions are the ...

- asked by MathLind (2 votes)

—————————-

[Wolfram math on windows using PBSPro cluster] http://mathematica.stackexchange.com/questions/125861/wolfram-math-on-windows-using-pbspro-cluster

A user wishes to use math application running on our PBSPpro cluster.

Our cluster is accessible to linux users, running qsub to submit their jobs.

We have math10.4 for our cluster users, with ...

- asked by Dvory (2 votes)

—————————-

[Unexpected view of a vectorial triad in a combination of a Plot3D with Graphics3D] http://mathematica.stackexchange.com/questions/126168/unexpected-view-of-a-vectorial-triad-in-a-combination-of-a-plot3d-with-graphics3

I am preparing an illustration for the lecture on differential geometry. In this demonstration I am illustrating the Monge parameterization of the surface:

R = {xx, yy, 55 + xx^2 - xx^3 - 2*yy^2}; (*  ...

- asked by Alexei Boulbitch (2 votes)

54 Tuesday, September 6, 2016

==================================
Top new questions this week:
==================================

[The Game of Hex in Mathematica] http://mathematica.stackexchange.com/questions/125460/the-game-of-hex-in-mathematica

The Game of Hex is a game originally developed by Nash, and it’s rules are very simple. You start out with a hexagonal tiling of some size:

There are two players. The game is in turns, and every ...

- asked by TreFox (31 votes), answered by C. E. (26 votes)

—————————-

[Visualize fraction] http://mathematica.stackexchange.com/questions/125209/visualize-fraction

I would like to visualize a fraction like the square root of 2 with Mathematica. I found this visualization of Pi in the internet and wonder how this would be done with Mathematica. The image shows ...

- asked by Arjihad (22 votes), answered by Kuba (20 votes)

—————————-

[Monad-like structures in Mathematica] http://mathematica.stackexchange.com/questions/125537/monad-like-structures-in-mathematica

I have been trying to code monad-like structures in Mathematica. However, I am facing some issues and I was wondering if anyone can help. I will give some background in the hope it can be useful to ...

- asked by Diogo Gomes (16 votes), answered by m_goldberg (6 votes)

—————————-

[paclets updating awareness and tracking] http://mathematica.stackexchange.com/questions/125199/paclets-updating-awareness-and-tracking

It turns out that some silent updating may be done in our computers with paclets. See for example here. How are we aware that something has been changed ? Can we track updating/versions of paclets ?

...

- asked by andre (16 votes)

—————————-

[Is it important that the front-end has a built-in parser?] http://mathematica.stackexchange.com/questions/125180/is-it-important-that-the-front-end-has-a-built-in-parser

The Notebook interface has a parser that seems aware of all operator-precedences, allowing us to step through the expressions (rather: Box-) hierarchy with Ctrl+.

This is extremely convenient, saving ...

- asked by masterxilo (15 votes), answered by John Fultz (18 votes)

—————————-

[Package organization] http://mathematica.stackexchange.com/questions/125579/package-organization

When writing a Mathematica package Foo, with functions f1, f2 and f3, one can use the template:

BeginPackage["Foo`"];

f1::usage = "f1[] ....";

f2::usage = "f2[] ....";

Begin["`Private`"];

f1[]:=  ...

- asked by Pixor (14 votes), answered by Szabolcs (17 votes)

—————————-

[ClearAll::clloc - ”Cannot clear local variable x” in Block[x, ...] - why?] http://mathematica.stackexchange.com/questions/125251/clearallclloc-cannot-clear-local-variable-x-in-blockx-why

Block[{x}, ClearAll@x]

  ClearAll::clloc: Cannot clear local variable x.

The documentation just says

An error occurs because ClearAll cannot be used with a local variable in Block:

and

...

- asked by masterxilo (14 votes)

================================== Greatest hits from previous weeks: ==================================

[Beautiful dance of the Earth and Venus around the sun] http://mathematica.stackexchange.com/questions/115358/beautiful-dance-of-the-earth-and-venus-around-the-sun

I have seen very nice dynamic graphics created by users of Ma. I would like to get help whether the following graphics can be created using Ma. I was not able to create the dynamic picture here. ...

- asked by ramesh (11 votes), answered by ubpdqn (6 votes)

—————————-

[How can I draw the Olympic rings with Mathematica?] http://mathematica.stackexchange.com/questions/8885/how-can-i-draw-the-olympic-rings-with-mathematica

How can I draw the 5 interlocking Olympic rings with Mathematica?

(SVG version)

Edit

Hard choice, but some pretty cool answers here. I didn’t have 3D answers in mind when I posted the question, ...

- asked by Mike Honeychurch (41 votes), answered by cormullion (18 votes)

================================== Can you answer these? ==================================

[Creating notebooks with specific options being editable but not saveable] http://mathematica.stackexchange.com/questions/125676/creating-notebooks-with-specific-options-being-editable-but-not-saveable

The goal

is to create a notebook whose options, when the notebook is opened, are fixed regardless of edits done to the notebook.

E.g. WindowSize -&gt; Automatic and WindowMargins -&gt; 30 should be  ...

- asked by Kuba (8 votes)

—————————-

[Possible bug with Dataset formatting for incompatible shapes and Missing] http://mathematica.stackexchange.com/questions/125689/possible-bug-with-dataset-formatting-for-incompatible-shapes-and-missing

Bug introduced in 11.0.0

The problem:

{&lt;|"a" -&gt; Range[5]|&gt;, &lt;|"a" -&gt; Missing["KeyAbsent", "a"]|&gt;} // Dataset

More detailed example shows that 5 is the magic number and ...

- asked by Kuba (10 votes)

—————————-

[TensorContract applied twice] http://mathematica.stackexchange.com/questions/125588/tensorcontract-applied-twice

I have a very simple question about TensorContract command: I’m declaring

$Assumptions = {T \[Element] Arrays[{4, 4, 4, 4}], a \[Element] Arrays[{4, 4}], b \[Element] Arrays[{4, 4}]};

so T is a ...

- asked by MaPo (3 votes)

55 Tuesday, August 30, 2016

==================================
Top new questions this week:
==================================

[How to make a Spherical Cow?] http://mathematica.stackexchange.com/questions/125043/how-to-make-a-spherical-cow

Being a theoretical physicist, I always have a great respect for Spherical Cow. So I thought about making one myself. I am not sure how can I create (something considered to be the simplest!) this ...

- asked by Sumit (29 votes), answered by andre (41 votes)

—————————-

[Unit Discovery: Is this some sort of a sick joke?] http://mathematica.stackexchange.com/questions/124745/unit-discovery-is-this-some-sort-of-a-sick-joke

Alright, let’s have some fun here. I am essentially following the documentation by Wolfram, just looking at different quantities.

N[UnitConvert[Quantity["earths gravity"]]]

9.80665m/(s)^2

Hmm, ...

- asked by Pirx (26 votes), answered by Xavier (27 votes)

—————————-

[Remove noise from data] http://mathematica.stackexchange.com/questions/124928/remove-noise-from-data

Hi, as you can see above I have some experimental data which has a large offset and shows clear noise fluctations around the tendency of the curve. I wanted to ask if someone could suggest me a ...

- asked by Filipe (23 votes), answered by nikie (22 votes)

—————————-

[Q&A Mathematica v.11 Neural Networks: A comprehensive look at Layers, Net Functions, and pioneering into this [[experimental]] code] http://mathematica.stackexchange.com/questions/124977/qa-mathematica-v-11-neural-networks-a-comprehensive-look-at-layers-net-functi

Motivation

As Mathematica v.11 was released earlier this month with a host of new [[experimental]] functions and a limited number of examples on curated data that do not cover all layers, options, ...

- asked by SumNeuron (20 votes), answered by Sebastian (12 votes)

—————————-

[Custom OpenerView with lazy evaluation] http://mathematica.stackexchange.com/questions/124892/custom-openerview-with-lazy-evaluation

OpenerView can be nested to create a hierarchical structure such as this:

One great aspect is that it remembers which lists are open and which are closed even after the parent has been closed and ...

- asked by C. E. (16 votes), answered by C. E. (7 votes)

—————————-

[RNN in Mathematica?] http://mathematica.stackexchange.com/questions/124988/rnn-in-mathematica

Recurrent neural network is an important part of machine learning and its improved version: LSTM network is widely applied, but Mathematica seemingly is in lack of these two features and in my ...

- asked by Wjx (15 votes), answered by Taliesin Beynon (19 votes)

—————————-

[Pentagonal spiral in Mathematica] http://mathematica.stackexchange.com/questions/125007/pentagonal-spiral-in-mathematica

I would like to plot an image of what I call a pentagonal spiral with Mathematica. A sample image of what I’d like to obtain is this (sorry for low-quality):

My initial idea was to get some kind of ...

- asked by bharb (14 votes), answered by Wjx (11 votes)

================================== Greatest hits from previous weeks: ==================================

[Labeling individual curves in Mathematica] http://mathematica.stackexchange.com/questions/4444/labeling-individual-curves-in-mathematica

I need to create a plot for export and inclusion in a report. Is there a better way to label curves than PlotLegends? From what I’ve read and my personal experience, PlotLegends is pretty bad.

Is ...

- asked by Tianxiang Xiong (44 votes), answered by Artes (37 votes)

—————————-

[How to make this beautiful animation] http://mathematica.stackexchange.com/questions/112700/how-to-make-this-beautiful-animation

How to make an animation of following gif in Mathematica?

Edit: The animation shown above was created by Charlie Deck in processing.

And how to make 3D analog?

I tried first few steps

line = ...

- asked by vito (45 votes), answered by C. E. (48 votes)

================================== Can you answer these? ==================================

[WolframScript never exits (v11 only)] http://mathematica.stackexchange.com/questions/124667/wolframscript-never-exits-v11-only

after updating to version 11, I came across a problem with the execution of package files via bash.

The WolframScript program runs the entire code, but frequently it does not exit properly and as a ...

- asked by fabio.hipolito (5 votes)

—————————-

[Representing inequalties with proper boundaries] http://mathematica.stackexchange.com/questions/124747/representing-inequalties-with-proper-boundaries

I have a very simple problem: given an inequality, I’d like to represent it in a regional plot marking the boundary differently depending whether it belongs to the region or not. For example I’d like ...

- asked by Geon (3 votes)

—————————-

[StringTemplate performance issue] http://mathematica.stackexchange.com/questions/125087/stringtemplate-performance-issue

StringTemplate introduced in version 10 is very convenient in constructing formatted data. However, it seems to have a huge performance issue.

Consider this example:

data = RandomInteger[1, 100, ...

- asked by xslittlegrass (5 votes)

56 Tuesday, August 23, 2016

==================================
Top new questions this week:
==================================

[GeoPosition coordinates from Shape file (.SHP) with unknown Datum] http://mathematica.stackexchange.com/questions/124121/geoposition-coordinates-from-shape-file-shp-with-unknown-datum

The City of Amsterdam supports an Open Data policy. Much information can be retrieved at the level of boroughs (stadsdelen). Unfortunately, GeoGraphics does not provide outlines of these smaller ...

- asked by Romke Bontekoe (12 votes), answered by JasonB (8 votes)

—————————-

[Detecting collisions in FEM] http://mathematica.stackexchange.com/questions/124324/detecting-collisions-in-fem

Say I want to study the deformation of a pitchfork when you have it fixed on the bottom and push one side.

&lt;&lt; NDSolve`FEM`
Ω =
  RegionDifference[Cuboid[{0, -5}, {1, 0}],
   Cuboid[{0.45,  ...

- asked by tsuresuregusa (12 votes)

—————————-

[Discovering crosswords] http://mathematica.stackexchange.com/questions/124552/discovering-crosswords

I am trying to create a code that can identify the following terms: MATHEMATICA, STACK, EXCHANGE and USERS.

list1={"M","S","T","A","S","I","S","X","X","T","R","X"};
list2={"A ","T ","H ","X ","R ","X  ...

- asked by Leandro Maciel de Carvalho (11 votes), answered by C. E. (15 votes)

—————————-

[29 Differential equations hang/not solved in version 11 compared to 10.4, looking for cause] http://mathematica.stackexchange.com/questions/124573/29-differential-equations-hang-not-solved-in-version-11-compared-to-10-4-lookin

I run Kamke differential equations in version 11 and compared the result to version 10.4. Found 29 differential equations that are no longer solved in version 11. Actually v11 hangs on these, eating ...

- asked by Nasser (11 votes)

—————————-

[Using predefined expressions as free variables in a pure function] http://mathematica.stackexchange.com/questions/124530/using-predefined-expressions-as-free-variables-in-a-pure-function

I want to have a function value of an expression where some variables are solutions to some set of equations, with some values of parameters. I had an idea to use pure functions for that.

However, ...

- asked by Picek (10 votes), answered by Alexey Popkov (4 votes)

—————————-

[How to delete unnecessary resistances in a resistance network] http://mathematica.stackexchange.com/questions/124475/how-to-delete-unnecessary-resistances-in-a-resistance-network

I’m still dealing with resistance network processing and got one problem left: how to delete unnecessary resistances?

Background

Let’s assume we are junior high students and know nothing about ...

- asked by Wjx (10 votes), answered by Sascha (5 votes)

—————————-

[Object detection in a low contrast image] http://mathematica.stackexchange.com/questions/124060/object-detection-in-a-low-contrast-image

I have a small dark object in the upper left corner of an image.

How can I separate it from the noisy rest and determine its IntensityCentroid?

The problem is that the objects intensity is not ...

- asked by mrz (10 votes), answered by Svyatoslav Korneev (12 votes)

================================== Greatest hits from previous weeks: ==================================

[Make a beautiful Moiré effect] http://mathematica.stackexchange.com/questions/112998/make-a-beautiful-moir%c3%a9-effect

How do I make the following Moiré pattern?

I tried:

A = Plot[Table[n, {n, 1, 30}], {x, 0, 31},
GridLines -&gt; {Table[n, {n, 1, 30}], None},
GridLinesStyle -&gt; AbsoluteThickness[1.2],  ...

- asked by vito (23 votes), answered by gpap (34 votes)

—————————-

[Beautiful dance of the Earth and Venus around the sun] http://mathematica.stackexchange.com/questions/115358/beautiful-dance-of-the-earth-and-venus-around-the-sun

I have seen very nice dynamic graphics created by users of Ma. I would like to get help whether the following graphics can be created using Ma. I was not able to create the dynamic picture here. ...

- asked by ramesh (11 votes), answered by ubpdqn (6 votes)

================================== Can you answer these? ==================================

[CapForm bugged in V11?] http://mathematica.stackexchange.com/questions/124591/capform-bugged-in-v11

It appears on my system (OSX 10.10.5) that CapForm isn’t behaving itself in V11. Initially I thought it was a problem with the combination of CapForm and VertexColors but it seems even weirder than ...

- asked by Quantum_Oli (6 votes)

—————————-

[Linear tangent steering law and orbital insertion altitude] http://mathematica.stackexchange.com/questions/124489/linear-tangent-steering-law-and-orbital-insertion-altitude

I’ve been trying to figure out how to build a rocket launch simulation that allows the user to specify the desired altitude at which a payload will be inserted into a stable circular orbit, but have ...

- asked by AlexR (2 votes)

—————————-

[What is a ”generic case”?] http://mathematica.stackexchange.com/questions/124347/what-is-a-generic-case

Introduction

With this question I am coming back to a long-standing issue I have with Mma’s concept of a ”generically correct” result. The basic idea seems to be, vaguely, that if a result is true in ...

- asked by Pirx (6 votes)

57 Tuesday, August 16, 2016

==================================
Top new questions this week:
==================================

[Can Mathematica put these puzzle pieces together?] http://mathematica.stackexchange.com/questions/123993/can-mathematica-put-these-puzzle-pieces-together

I have five DXF files with various geometric figures.

Are squares with a different geometric shape in each DXF file...

Four DXF files have a square with a different geometric shape on one side ...

- asked by Leandro Maciel de Carvalho (17 votes), answered by kirma (11 votes)

—————————-

[How to monitor the process of Neural Network Learning] http://mathematica.stackexchange.com/questions/123684/how-to-monitor-the-process-of-neural-network-learning

Main Problem

I’m exploring the neural network in v11 and I would like to monitor the training progress in my own way instead of Mathematica’s default way. So my question is, how to do this ...

- asked by Wjx (17 votes), answered by Taliesin Beynon (13 votes)

—————————-

[Changes to Coefficient function in v10.2] http://mathematica.stackexchange.com/questions/123565/changes-to-coefficient-function-in-v10-2

In the version Mathemaica 10.4, I am very surprised that the core function Coefficient has changed, e.g.,

Coefficient[3 x x + 8 y y - 24 x y, 2 x y]

  0

In previous versions (e.g. v9.0.1, ...

- asked by Orders (17 votes)

—————————-

[Unexpected behaviour from Table[]] http://mathematica.stackexchange.com/questions/124046/unexpected-behaviour-from-table

The following code in Mathematica 11:

iList = {i, -10, 10, 2};
Table[i, iList]


produces this result:

{i, i, i, i}

Where in version 10 (and presumably earlier versions) it produced an error:

...

- asked by Bruce Crawford (16 votes), answered by Szabolcs (15 votes)

—————————-

[Can Mathematica act like a web server?] http://mathematica.stackexchange.com/questions/123805/can-mathematica-act-like-a-web-server

I have a Mathematica program that modifies images that I would like to make available for other people to use through the web. The input is only one parameter. So, for example, I could run it as a ...

- asked by Tyler Durden (16 votes)

—————————-

[How to generate all possible orderless partitions of a list according to another list?] http://mathematica.stackexchange.com/questions/123835/how-to-generate-all-possible-orderless-partitions-of-a-list-according-to-another

This question is hard to describe in plain text. So I will post an example and a working code (brute force) to illustrate.

For example I have a list: {1, 2, 3, 4, 5} and a partition list {2, 2, 1}. I  ...

- asked by happy fish (15 votes), answered by Mr.Wizard (11 votes)

—————————-

[RandomPoint crashes kernel] http://mathematica.stackexchange.com/questions/123735/randompoint-crashes-kernel

Bug introduced in Version 11.0

Reported as CASE:3686963, 12 Aug 2016

I attempted to determine whether the problem with RandomPoint identified in my answer to question 89384 had been fixed in

...

- asked by bbgodfrey (12 votes), answered by ilian (6 votes)

================================== Greatest hits from previous weeks: ==================================

[How to Plot an Infinite Series] http://mathematica.stackexchange.com/questions/14083/how-to-plot-an-infinite-series

I want to sketch the graphs of

         1-  ∑   1--    n      −n2t
u (t,x) = 2 +     nπ((− 1) − 1)e    sin(nx )
             n≥1
for t = 0,0.01,0.1,0.5,1,10  on the same axes.

For t = 0  , I input

Plot[{1/2 +  ...

- asked by Vladimir (2 votes), answered by chris (9 votes)

—————————-

[How to make this beautiful animation] http://mathematica.stackexchange.com/questions/112700/how-to-make-this-beautiful-animation

How to make an animation of following gif in Mathematica?

Edit: The animation shown above was created by Charlie Deck in processing.

And how to make 3D analog?

I tried first few steps

line = ...

- asked by vito (45 votes), answered by C. E. (48 votes)

================================== Can you answer these? ==================================

[Holidays output] http://mathematica.stackexchange.com/questions/123763/holidays-output

I wanted to print out the holidays in Germany in 2016:

DayRange[DateObject[{2016, 1, 1}],
 DateObject[{2016, 12, 31}], "Holiday",
 HolidayCalendar -&gt; {"Germany", "Bavaria"}]

The result list ...

- asked by mrz (2 votes)

—————————-

[How to crawl some website needed username and password] http://mathematica.stackexchange.com/questions/123771/how-to-crawl-some-website-needed-username-and-password

In version 11,if we want to crawl public website like wiki,we can do it like this:

URLRead["https://en.wikipedia.org/wiki/Wiki", "Body"]

But I don’t know how to crawl some website needed ...

- asked by yode (4 votes)

—————————-

[NFourierTransform of an interpolating function] http://mathematica.stackexchange.com/questions/123800/nfouriertransform-of-an-interpolating-function

I have an interpolating function called rs22 - a solution from NDSolve - which is defined from 0 to about 1 ms. rs22 is a function that reaches a non-zero equilibrium value. (only shown here up to ...

- asked by Shiki (3 votes)

58 Tuesday, August 9, 2016

==================================
Top new questions this week:
==================================

[PostScript-like drawing in Mathematica?] http://mathematica.stackexchange.com/questions/123289/postscript-like-drawing-in-mathematica

To illustrate by example, construct an equilateral triangle in PostScript:

0 0 moveto           %moveto origin
6 0 lineto           %construct first line segment
6 0 translate        %translate  ...

- asked by Alan (14 votes), answered by WReach (21 votes)

—————————-

[Efficiently exchange elements between two lists] http://mathematica.stackexchange.com/questions/123221/efficiently-exchange-elements-between-two-lists

I have two lists with equal length, and I want to exchange the elements on every even positions. For example,

{{1, 2, 3, 4, 5}, {6, 7, 8, 9, 10}}


will return

{{1, 7, 3, 9, 5}, {6, 2, 8, 4, 10}}

 ...

- asked by happy fish (13 votes), answered by Kuba (12 votes)

—————————-

[Finite element simulation of Airy waves] http://mathematica.stackexchange.com/questions/122063/finite-element-simulation-of-airy-waves

I am attempting to solve for waves on a water surface starting with a two dimensional solution. The equations are that the water must satisfy Laplace’s equation everywhere with a time dependent ...

- asked by Hugh (13 votes), answered by user21 (10 votes)

—————————-

[How do you make a Neural Net?] http://mathematica.stackexchange.com/questions/123458/how-do-you-make-a-neural-net

In the new Mathematica release (v11), NeuralNetworks is one of the new main features. However, the documentation isn’t that clear on what function should be used in a Net.

The documentation on ...

- asked by JHM (12 votes), answered by Searke (13 votes)

—————————-

[How to plot data by counties?] http://mathematica.stackexchange.com/questions/123324/how-to-plot-data-by-counties

I’d like to plot county data as in this D3 example:

Is there a way to do this with GeoGraphics, or at least to get path polygons per county and then plot them with different colors?

The first ...

- asked by M.R. (11 votes), answered by C. E. (9 votes)

—————————-

[Why are delayed definitions in scoping functions NOT documented?] http://mathematica.stackexchange.com/questions/122061/why-are-delayed-definitions-in-scoping-functions-not-documented

As outlined here, := may be used in scoping constructs like With to give delayed definitions, but this is undocumented.

This has been in the language since at least Mathematica 4.0. It is very ...

- asked by Mr.Wizard (11 votes)

—————————-

[Shading under a curve with dots]http://mathematica.stackexchange.com/questions/123422/shading-under-a-curve-with-dots

I plotted the function y = x2   using the Plot command

Plot[x^2, {x,-5,5}]

I need to shade the area under the curve using a pattern (dots pattern), not using a solid color or a hue. Is it possible? ...

- asked by James (10 votes), answered by JasonB (14 votes)

================================== Greatest hits from previous weeks: ==================================

[General strategies to write big code in Mathematica?] http://mathematica.stackexchange.com/questions/109888/general-strategies-to-write-big-code-in-mathematica

I think after six months of exposure to Mathematica and the Wolfram Language I am fairly OK with writing short codes and snippets. However, what are some general strategies to use in order to write ...

- asked by Ali Hashmi (94 votes), answered by Leonid Shifrin (75 votes)

—————————-

[Where can I find examples of good Mathematica programming practice?] http://mathematica.stackexchange.com/questions/18/where-can-i-find-examples-of-good-mathematica-programming-practice

I consider myself a pretty good Mathematica programmer, but I’m always looking out for ways to either improve my way of doing things in Mathematica, or to see if there’s something nifty that I haven’t ...

- asked by J. M. (430 votes), answered by faysou (388 votes)

================================== Can you answer these? ==================================

[Can I use Mathematica as a constraint solver?] http://mathematica.stackexchange.com/questions/123487/can-i-use-mathematica-as-a-constraint-solver

I have been using SMT solvers for program analysis. Basically the idea is to translate x86 assembly code to SMT formulas and use the solver for automatic input test generation. There is a Microsoft ...

- asked by Edgar (1 vote)

—————————-

[Why is this function slower after a simple change?] http://mathematica.stackexchange.com/questions/122109/why-is-this-function-slower-after-a-simple-change

I have a function that calculates the rank of a restricted growth string defined like so,

rankKRGS[{}] = 0;
rankKRGS[string_] :=
 With[{n = Length@string, k = Max@string + 1, alone =  ...

- asked by Jordy Dickinson (3 votes)

—————————-

[Is there an efficient way to monitor the progress of a task remotely?] http://mathematica.stackexchange.com/questions/123181/is-there-an-efficient-way-to-monitor-the-progress-of-a-task-remotely

Recently, I’ve been running Mathematica packages on a remote cluster using SSH (using, e.g. the command

nohup nice math -noprompt -run "&lt;&lt;myPackage.m" &gt; myOutput &amp;

so that the output ...

- asked by Nikhil Anand (2 votes)

59 Tuesday, August 2, 2016

==================================
Top new questions this week:
==================================

[How can I detect locations of Go (aka Baduk, Weiqi) stones on a board?] http://mathematica.stackexchange.com/questions/121835/how-can-i-detect-locations-of-go-aka-baduk-weiqi-stones-on-a-board

The Goal

There are a couple apps that score a Go board from a photo. I was wondering if something like that would be possible with Mathematica. The key step is to detect the positions of the stones ...

- asked by Mark S. (19 votes), answered by halirutan (2 votes)

—————————-

[What are all the ”magic” Symbols in the Mathematica language?] http://mathematica.stackexchange.com/questions/121981/what-are-all-the-magic-symbols-in-the-mathematica-language

Leonid Shifrin once wrote (excerpted):

(Unevaluated) is one of a very few ”magic symbols”, along with Sequence and Evaluate - these are deeply wired into the system and can not be easily ...

- asked by Mr.Wizard (16 votes), answered by Mr.Wizard (9 votes)

—————————-

[What has changed in pattern matching functions with the Orderless attribute?] http://mathematica.stackexchange.com/questions/121564/what-has-changed-in-pattern-matching-functions-with-the-orderless-attribute

In making an attempt to answer this question, we ran into a version-dependent pattern-matching issue. An extended discussion in the comments transpired, and some inconsistencies arose. Consider the ...

- asked by march (16 votes)

—————————-

[Converting a Sierpinski tetrahedron to a Graph] http://mathematica.stackexchange.com/questions/121553/converting-a-sierpinski-tetrahedron-to-a-graph

I need a representation of a 3D Sierpinski gasket as a graph to perform some simulations on. The 2D version is included in GraphData[], but the 3D one is nowhere to be found, so I was wondering if ...

- asked by FEARxxx (13 votes), answered by J. M. (2 votes)

—————————-

[Working with DynamicModule: SetDelayed + OwnValues] http://mathematica.stackexchange.com/questions/121584/working-with-dynamicmodule-setdelayed-ownvalues

Shortly, definitions in form of e.g. x:= RandomReal[] have to be avoided
inside DynamicModule[{x}, ...]. Why?, this Prints immediately:

DynamicModule[{x}, x := Print[1]; {}]

It hit us hard in the ...

- asked by Kuba (12 votes), answered by Kuba (13 votes)

—————————-

[How to speed up pattern matching] http://mathematica.stackexchange.com/questions/121911/how-to-speed-up-pattern-matching

Main Problem

Mr.Wizard posed this question when discussing another problem.

I reproduce the main part of Mr.Wizard’s problem here:

MatchQ[{1, 2, 3, 4, 5}, {x__?((Echo[##]; False) &amp;), y__}]

On ...

- asked by Wjx (11 votes), answered by Michael E2 (5 votes)

—————————-

[How to efficiently implement k-FN (k-Furthest Neighbors)?] http://mathematica.stackexchange.com/questions/121541/how-to-efficiently-implement-k-fn-k-furthest-neighbors

I’d like to pick k points from a set of points in n-dimensions that are approximately ”maximally apart” (sum of pairwise distances is almost maxed). What is an efficient way to do this in MMA? Using ...

- asked by M.R. (10 votes), answered by C. Woods (2 votes)

================================== Greatest hits from previous weeks: ==================================

[Writing a word with straight lines] http://mathematica.stackexchange.com/questions/113403/writing-a-word-with-straight-lines

Here is an interesting way to write a word: (it is from a poster for the International Museum Day 2006; I believe it even won an award at an international design competition)

by Boris Ljubicic. ...

- asked by VividD (70 votes), answered by Anton Antonov (32 votes)

—————————-

[Make a beautiful Moiré effect] http://mathematica.stackexchange.com/questions/112998/make-a-beautiful-moir%c3%a9-effect

How do I make the following Moiré pattern?

I tried:

A = Plot[Table[n, {n, 1, 30}], {x, 0, 31},
GridLines -&gt; {Table[n, {n, 1, 30}], None},
GridLinesStyle -&gt; AbsoluteThickness[1.2],  ...

- asked by vito (23 votes), answered by gpap (34 votes)

================================== Can you answer these? ==================================

[Looking for a package for finite mappings] http://mathematica.stackexchange.com/questions/121776/looking-for-a-package-for-finite-mappings

I am looking for a package for dealing with ”mappings” f: A → B  where A  and B  are finite subsets of the set of all possible (inert) expressions.

I need operations like:

Computing f (a )  ...

- asked by masterxilo (3 votes)

—————————-

[Using Palettes in Mathematica Online] http://mathematica.stackexchange.com/questions/121935/using-palettes-in-mathematica-online

my student is using the online version of Mathematica for my class; it appears to not have a palette feature for typing formatted input? This was kind of shocking to me; why wouldn’t there be a ...

- asked by Jake Mirra (1 vote)

—————————-

[Derivation of an interpolation function with multiple arguments] http://mathematica.stackexchange.com/questions/121599/derivation-of-an-interpolation-function-with-multiple-arguments

I have the following interpolation function:

f[x_,a_,b_]:=70 s[a,b][[1,1,2]][x]


where s[a,b] is the solution of a differential equation.

s[a_, b_] := NDSolve[{
   H2[x] == Rx[x]^2 + G[x, a, b],
   ...

- asked by Maria (2 votes)

60 Tuesday, July 26, 2016

==================================
Top new questions this week:
==================================

[Generate a certain colorful triangle] http://mathematica.stackexchange.com/questions/121353/generate-a-certain-colorful-triangle

I want to get a colorful triangle like this:

I hope to get a triangle with any number of layers. This is my current method. Actually, I’m not very content with these graph theory functions, since ...

- asked by yode (13 votes), answered by Mr.Wizard (7 votes)

—————————-

[Bad interaction between Join and ListPlot (or Plot)] http://mathematica.stackexchange.com/questions/121289/bad-interaction-between-join-and-listplot-or-plot

When you write this code:

tab = {{1, 1}}; tab = Join[tab, {{2,2}}];


you expect to get the following table:

{{1, 1}, {2, 2}}


but, if you write the following code instead:

tab = {{1, 1}}; tab =  ...

- asked by Francisco (11 votes), answered by C. E. (8 votes)

—————————-

[Handwriting recognition with Mathematica] http://mathematica.stackexchange.com/questions/121051/handwriting-recognition-with-mathematica

I am trying to teach Mathematica to read my handwriting. Since I don’t want to ruin my reputation by showing my own handwriting, I am going to use a font called blackjack.

Lets say this is a ...

- asked by Sumit (11 votes)

—————————-

[Can one effectively edit a Front End Resource that is already loaded?] http://mathematica.stackexchange.com/questions/121059/can-one-effectively-edit-a-front-end-resource-that-is-already-loaded

A number of special definitions are loaded from .tr files on Front End initialization and are accessible via FrontEndResource. These are used among other things for various menus and toolsbars, e.g.:

- asked by Mr.Wizard (11 votes)

—————————- [Bug with Compile and Log2?] http://mathematica.stackexchange.com/questions/121336/bug-with-compile-and-log2

It seems that Log2 in Compile gives numerical errors (CompiledFunction::cfn) if the input is not a power of 2.

For instance:

test1 = Compile[{{in, _Integer}}, Log2[in]];
test1[3]

gives an error ...

- asked by JHM (10 votes), answered by Michael E2 (4 votes)

—————————-

[What is the effect of giving ColorFunctionScaling a numerical argument?] http://mathematica.stackexchange.com/questions/121231/what-is-the-effect-of-giving-colorfunctionscaling-a-numerical-argument

(by making a mistake) I realised that ColorFunctionScaling can take a list of numerical arguments rather than just booleans. The following is true for ContourPlot and DensityPlot but not Plot3D and ...

- asked by gpap (10 votes), answered by Mr.Wizard (4 votes)

—————————-

[Reproducing the xkcd ”Self-Description” comic] http://mathematica.stackexchange.com/questions/121160/reproducing-the-xkcd-self-description-comic

Trying to brush up on my programming, I wanted to see if I can reproduce at least the first two panels of the following comic in Mathematica:

I have some code for trying to reproduce the first ...

- asked by Mayumi Ito (10 votes), answered by Alexey Popkov (7 votes)

================================== Greatest hits from previous weeks: ==================================

[Exporting graphics to PDF - huge file] http://mathematica.stackexchange.com/questions/1542/exporting-graphics-to-pdf-huge-file

I want to draw some basic surfaces, export them to PDF and include them in a LaTeX file. I create a simple 3D graphics object, for instance with

 ParametricPlot3D[{r Cos[\[Theta]], r Sin[\[Theta]],  ...

- asked by Matthew Leingang (84 votes), answered by Heike (71 votes)

—————————-

[Calculate the 2D Fourier transform of an Image] http://mathematica.stackexchange.com/questions/29203/calculate-the-2d-fourier-transform-of-an-image

I am new to Mathematica, and using version 8.0.

I would like to calculate the 2D Fourier Transform of an Image with Mathematica and plot the magnitude and phase spectrum, as well as reconstruct the ...

- asked by user8727 (2 votes), answered by Nasser (22 votes)

================================== Can you answer these? ==================================

[single slit diffraction numerical simulation] http://mathematica.stackexchange.com/questions/121474/single-slit-diffraction-numerical-simulation

I’m trying to simulate the Fraunhoffer diffraction at slits(single,double,triple) with Mathematica.

In the picture, the red one is analytical result and the green one is numerical result.

The ...

- asked by Taeshin Kim (5 votes)

—————————-

[How does the Contours-¿f_1, g1, f_2, g_2,... setting work?] http://mathematica.stackexchange.com/questions/121205/how-does-the-contours%e2%86%92f-1-g1-f-2-g-2-setting-work

I want to plot some wavefronts in Mathematica, and I’m having some trouble reining in one of the options for my ContourPlot3D.

More specifically, the documentation for ContourPlot3D says that the ...

- asked by Emilio Pisanty (5 votes)

—————————-

[Is every menu command equivalent to a command that can be executed within a notebook?] http://mathematica.stackexchange.com/questions/121453/is-every-menu-command-equivalent-to-a-command-that-can-be-executed-within-a-note

If so, is there a directory which gives the in-notebook command associated with each menu command ?

In particular, I would like to know how to replicate the
menu command Evaluation -> Quit Kernel ->  ...

- asked by Simon (3 votes)

61 Tuesday, July 19, 2016

==================================
Top new questions this week:
==================================

[How can I better mimic the graphics at earth.nullschool.net?] http://mathematica.stackexchange.com/questions/120842/how-can-i-better-mimic-the-graphics-at-earth-nullschool-net

I’d like to be able to better mimic the graphics at earth.nullschool.net using Mathematica and I’m looking for suggestions for either improving my code or getting directed to some other approach.

...

- asked by Jim Baldwin (14 votes), answered by Simon Woods (15 votes)

—————————-

[how to permute list of number1,2,3,...,n,while preserve the order of first m terms as well as the last n-m terms?] http://mathematica.stackexchange.com/questions/120690/how-to-permute-list-of-number1-2-3-n-while-preserve-the-order-of-first-m-t

For example, starting from 1,2,3,4, I want to generate all permutations like 1,3,2,4,1,3,4,2,3,4,1,2 which preserve the order of e.g first two terms 1,2 and the order of e.g. last two terms ...

- asked by user41614 (12 votes), answered by Kuba (8 votes)

—————————-

[Create a polynomial of a given degree] http://mathematica.stackexchange.com/questions/120841/create-a-polynomial-of-a-given-degree

In Mathematica, how can I create a polynomial function in given variables of a given degree with unknown coefficents?

That is, I am looking for a function Poly[vars, degree] that generates, for ...

- asked by Posch79 (11 votes), answered by march (6 votes)

—————————-

[Fractal basins of attraction in a Magnetic Pendulum] http://mathematica.stackexchange.com/questions/120946/fractal-basins-of-attraction-in-a-magnetic-pendulum

I am trying to write a Mathematica program that realizes a graphical approximation of the basins of attraction in a Magnetic pendulum subject to friction and gravity, in which the three magnets are ...

- asked by bharb (10 votes), answered by C. E. (9 votes)

—————————-

[Draw half empty rectangle] http://mathematica.stackexchange.com/questions/120781/draw-half-empty-rectangle

How can I draw an half or a third filled rectangle? I want to make one rectangle frame with a unity width and then filled it according to a value between 0 and 1.

- asked by Miguel (9 votes), answered by Feyre (9 votes)

—————————-

[How to access ”Choose Color Scheme” Programmatically] http://mathematica.stackexchange.com/questions/120999/how-to-access-choose-color-scheme-programmatically

I am designing an App and I want to use the ”Choose Color Scheme” tools inside Button.

I am looking to have this tool in popup window when the Button is clicked but I can’t find the command to get ...

- asked by Algohi (8 votes), answered by Karsten 7. (9 votes)

—————————-

[Programming the fiver game] http://mathematica.stackexchange.com/questions/120959/programming-the-fiver-game

Obviously, even if I ask a lot of question I am, obviously, still a dummy!!!!

I want to program the fiver game. It’s a very simple game played solitary on a 5× 5  the rule is elementary : if ...

- asked by cyrille.piatecki (8 votes), answered by Mr.Wizard (15 votes)

================================== Greatest hits from previous weeks: ==================================

[Creating 3D dice] http://mathematica.stackexchange.com/questions/110295/creating-3d-dice

How to create an image of a 3D die from the 2D images?

There is an example in the Documentation Center

I tried

but it doesn’t work.

- asked by vito (13 votes), answered by Martin Ender (21 votes)

—————————-

[xkcd-style graphs] http://mathematica.stackexchange.com/questions/11350/xkcd-style-graphs

I received an email to which I wanted to respond with a xkcd-style graph, but I couldn’t manage it. Everything I drew looked perfect, and I don’t have enough command over PlotLegends to have these ...

- asked by Amatya (518 votes), answered by Simon Woods (371 votes)

================================== Can you answer these? ==================================

[How to increase the image resolution of a map?] http://mathematica.stackexchange.com/questions/120572/how-to-increase-the-image-resolution-of-a-map

I’d like to obtain higher-resolution geographic maps retrieved from Wolfram geo server, since the standard resolution seems poor.

I tried to increase the ”TileSize” parameter, like this:

...

- asked by Fred (2 votes)

—————————-

[Hidden Markov Model: emissions probabilities dependent on observable parameter] http://mathematica.stackexchange.com/questions/120700/hidden-markov-model-emissions-probabilities-dependent-on-observable-parameter

I need to fit an HMM where the emission probabilities (ep) are discrete and dependent on a known variable quantity. E.g.:

Imagine a daily time series of binary emissions (”1” or ”2”). I suppose an ...

- asked by CupiDio (1 vote)

—————————-

[Why are there these jagged ”shards” in my RegionPlot3D?] http://mathematica.stackexchange.com/questions/120712/why-are-there-these-jagged-shards-in-my-regionplot3d

I’m creating a region out of two component regions. Before anyone suggests it (because a lot of similar questions are about it), I don’t think the problem is increasing PlotPoints. I’ve increased it ...

- asked by YungHummmma (1 vote)

62 Tuesday, July 12, 2016

==================================
Top new questions this week:
==================================

[How to extract the list of all matrices from a Block Diagonal Matrix?] http://mathematica.stackexchange.com/questions/120433/how-to-extract-the-list-of-all-matrices-from-a-block-diagonal-matrix

I am working on a function to do the opposite operation of How to form a block-diagonal Matrix from a list of matrices?

Here is my current algorithm: For i starting at 1, scan the elements of index ...

- asked by happy fish (11 votes), answered by yode (6 votes)

—————————-

[Collect all inputs from Documentation Center] http://mathematica.stackexchange.com/questions/120334/collect-all-inputs-from-documentation-center

Is it possible to collect all inputs programmatically from every function in the Documentation Center in a list and wrap them in a HoldComplete?

My case: With some fundamental functions modified, I ...

- asked by happy fish (9 votes), answered by Edmund (12 votes)

—————————-

[How to avoid procedural loops in this example?] http://mathematica.stackexchange.com/questions/120533/how-to-avoid-procedural-loops-in-this-example

I want to iterate over a list, and return the index as long as I found the first element satisfying my condition. Written in a for loop:

f[x_]:=2x

For[i=1, i&lt;=10, i++,
  If[f[i]==10, Return[i]]
]
 ...

- asked by Nick (8 votes), answered by Gerli (5 votes)

—————————-

[Why does this LibraryLink function crash?] http://mathematica.stackexchange.com/questions/120384/why-does-this-librarylink-function-crash

Recently, I have rewritten pure Wolfram Language implementation CAGDBSplineSurface[] with C. Below is main LibraryLink code:

LibraryLink Code

#include "WolframLibrary.h"

 ...

- asked by Shutao TANG (8 votes), answered by happy fish (11 votes)

—————————-

[How can I combine a list of Line[]’s into one continuous Line?] http://mathematica.stackexchange.com/questions/120285/how-can-i-combine-a-list-of-lines-into-one-continuous-line

I have a huge list of Lines. Take this one as an example:

linelist1 = {Line[{{0.15042300130733277`,
      0.09918669845167598`}, {0.15124668865085406`,
      0.09522452324491057`}}],
    ...

- asked by YungHummmma (8 votes), answered by Michael E2 (12 votes)

—————————-

[NIntegrate appears to give incorrect results] http://mathematica.stackexchange.com/questions/120118/nintegrate-appears-to-give-incorrect-results

I am trying to specify a bivariate probability density function in Mathematica. As a check, I would like to confirm that it integrates to one. Here is the function:

f[x1_, x2_, u1_, u2_, v11_, v22_,  ...

- asked by Miguel (8 votes), answered by Anton Antonov (11 votes)

—————————-

[Which fonts are supported in Wolfram Cloud?] http://mathematica.stackexchange.com/questions/120102/which-fonts-are-supported-in-wolfram-cloud

I recently suggested creating dynamic community ads with Wolfram Cloud. @C.E. made a proof of concept ad to show that it works well.

Fonts are an important part of graphics design. It is useful to ...

- asked by Szabolcs (8 votes), answered by Szabolcs (5 votes)

================================== Greatest hits from previous weeks: ==================================

[What is the best Mathematica tutorial for young people?] http://mathematica.stackexchange.com/questions/733/what-is-the-best-mathematica-tutorial-for-young-people

As Conrad Wolfram said at the TED conference, in the future kids should focus more on new technology. Computers compute better than humans, so we should focus more on thinking and getting the ...

- asked by noisy (44 votes), answered by Vitaliy Kaurov (23 votes)

—————————-

[Mathematica Minecraft] http://mathematica.stackexchange.com/questions/19669/mathematica-minecraft

Some time ago I asked myself: with all these great graphics and interactive capabilities of Mathematica, what kinds of 3D games can be implemented in it? And the answer which came to mind is ...

- asked by faleichik (140 votes), answered by faleichik (192 votes)

================================== Can you answer these? ==================================

[integrate giving wrong result] http://mathematica.stackexchange.com/questions/120495/integrate-giving-wrong-result

A question with the same title has been asked many times, but I can’t find the solution of my problem in their answers. The integral I am trying to calculate is

Integrate[Sin[q ]^2 / Sinh[q]^2, {q,  ...

- asked by Felix (7 votes)

—————————-

[Why FinancialDerivative fails for the Spread case?] http://mathematica.stackexchange.com/questions/120277/why-financialderivative-fails-for-the-spread-case

According to the documentation center for FinancialDerivative in version 10.4, when there are multi assets, we still may use FinancialDerivative with the corresponding correlation matrix to find the ...

- asked by M.J.2 (2 votes)

—————————-

[What does the GraphLayout -¿ ”SpectralEmbedding” option do (mean) when displaying a graph?] http://mathematica.stackexchange.com/questions/120139/what-does-the-graphlayout-spectralembedding-option-do-mean-when-displayin

I have some relational data represented as a graph. As such some of the relational properties can be recognized. When I use the GraphLayout -¿ ”SpectralEmbedding” option a very nice and sharply ...

- asked by Phillip Dukes (5 votes)

63 Tuesday, July 5, 2016

==================================
Top new questions this week:
==================================

[Which Object-oriented paradigm approach to use in Mathematica?] http://mathematica.stackexchange.com/questions/119991/which-object-oriented-paradigm-approach-to-use-in-mathematica

Which Object-Oriented Paradigm (OOP) approach to use in Mathematica for:

general implementation, or a particular project?

There are a lot of related questions and answers in MSE on doing OOP that ...

- asked by Anton Antonov (14 votes)

—————————-

[How can I use Mathematica to sort the US Congressional Districts by Perimeter÷Area] http://mathematica.stackexchange.com/questions/119944/how-can-i-use-mathematica-to-sort-the-us-congressional-districts-by-perimeter%c3%b7ar

The United States is divided into 435 congressional districts. Some of their shapes can be really strange due to gerrymandering. I think that I can find very gerrymandered congressional districts if ...

- asked by QuantumDot (13 votes), answered by Emilio Pisanty (6 votes)

—————————-

[Gillespie Stochastic Simulation Algorithm] http://mathematica.stackexchange.com/questions/119786/gillespie-stochastic-simulation-algorithm

The Gillespie SSA is a Monte Carlo stochastic simulation algorithm to find the trajectory a dynamic system described by a reaction (or interaction) network, e.g. chemical reactions or ecological ...

- asked by István Zachar (13 votes), answered by István Zachar (15 votes)

—————————-

[How to create a fascinating QR code like this?] http://mathematica.stackexchange.com/questions/120041/how-to-create-a-fascinating-qr-code-like-this

Check the facinating QRCode in my profile page here

You can find that this QRCode is some sort of intriguing as the QRCode is a IMAGE ITSELF!!!

So my question is, how to create such a QRCode ...

- asked by Wjx (11 votes), answered by Wjx (11 votes)

—————————-

[Data extraction from a picture of a graph] http://mathematica.stackexchange.com/questions/119666/data-extraction-from-a-picture-of-a-graph

How can I extract data from this picture of a graph?

i = Import["http://i.stack.imgur.com/Ac8m0.png"];

The caption of the picture reads: ” Two-dimensional histogram values measured . Tick labels ...

- asked by psimeson (10 votes), answered by Simon Woods (16 votes)

—————————-

[Evaluating summations involving Fibonacci numbers in terms of Fibonacci numbers] http://mathematica.stackexchange.com/questions/119822/evaluating-summations-involving-fibonacci-numbers-in-terms-of-fibonacci-numbers

There are many summations involving Fibonacci numbers which Mathematica 10.4 is able to evaluate directly in terms of Fibonacci numbers. For example, Mathematica evaluates the summation given below as ...

- asked by John M. Campbell (9 votes), answered by yarchik (4 votes)

—————————-

[TreeForm outputs different results for the same inputs but why?] http://mathematica.stackexchange.com/questions/119745/treeform-outputs-different-results-for-the-same-inputs-but-why

First of all, please look at the below inputs and outputs:

In[1]:= $a = Array[# Range[#] &amp;, {5}]

Out[1]= {{1}, {2, 4}, {3, 6, 9}, {4, 8, 12, 16}, {5, 10, 15, 20, 25}}

In[2]:= $af = Flatten[$a,  ...

- asked by Taiki Bessho (8 votes), answered by JasonB (11 votes)

================================== Greatest hits from previous weeks: ==================================

[How to plot an ellipse?] http://mathematica.stackexchange.com/questions/20100/how-to-plot-an-ellipse

I’m new to Mathematica, and I’m finding it difficult to plot an ellipse. I tried using

Plot[(x/5)^2 + (y/3)^2 == 1, {x, -5, 5}, {y, -3, 3}]

but I’m getting some errors. Is there something wrong ...

- asked by Sriram (6 votes), answered by Jens (15 votes)

—————————-

[Is it possible to draw this figure using Mathematica?] http://mathematica.stackexchange.com/questions/110848/is-it-possible-to-draw-this-figure-using-mathematica

The figure is

See the how-to video or a speeded-up GIF.

I believe it should be possible to draw this figure programmatically using some Random function, but I’m rather new to Mathematica, so I ...

- asked by AccidentalFourierTransform (50 votes), answered by M.R. (75 votes)

================================== Can you answer these? ==================================

[Hide Notebook scrollbars] http://mathematica.stackexchange.com/questions/119665/hide-notebook-scrollbars

Is it possible to hide the scrollbars from the notebook windows while still being able to use the mousewheel to scroll? Since I never click on the bars themselves they’re just a waste of space. It’s ...

- asked by Ray (3 votes)

—————————-

[Hold Values of DensityPlot to use for an other DensityPlot] http://mathematica.stackexchange.com/questions/120022/hold-values-of-densityplot-to-use-for-an-other-densityplot

I have two surface functions, f[x,y] and g[x,y]. Assuming that the DensityPlot of f and g takes a while, is there a way to hold the values of DensityPlot, to efficiently DensityPlot f[x,y]-g[x,y] ?

...

- asked by Pierre L. (1 vote)

—————————-

[How to place window on second screen?] http://mathematica.stackexchange.com/questions/119835/how-to-place-window-on-second-screen

I am trying to open a window on a second screen (a thunderbolt display attached to a macbook pro) that is the full size of the second screen. Here is the command I use:

ThunderboltDimensions = 2560, ...

- asked by abwatson (1 vote)

64 Tuesday, June 28, 2016

==================================
Top new questions this week:
==================================

[Is the renaming mechanism of ‘With‘ flawed?] http://mathematica.stackexchange.com/questions/119403/is-the-renaming-mechanism-of-with-flawed

I’m confused about the renaming mechanism of With:

With[{x = a}, Hold[With[{a = b}, a + 2 x]]]
(*==&gt;Hold[With[{a$ = b}, a$ + 2 a]]*)

With[{x = a$}, Hold[With[{a = b}, a + 2 x]]]
 ...

- asked by luyuwuli (21 votes), answered by Leonid Shifrin (22 votes)

—————————-

[How do I increase the readability of this code?] http://mathematica.stackexchange.com/questions/119074/how-do-i-increase-the-readability-of-this-code

Below is some code I am working on; being a beginner. How can I increase the readability of the part behind Manipulate?

I can’t read my own code anymore, because it is simply too long and unordered. ...

- asked by Imre Vegh (20 votes), answered by E.Doroskevic (16 votes)

—————————-

[Mysterious behaviour of Pick] http://mathematica.stackexchange.com/questions/119223/mysterious-behaviour-of-pick

As everyone knows, Pick can do amazing things, The most facinating phenomenon is that it can pick though all sorts of lists:

The basic &amp; pattern matching:

Pick[{4, 5, 6}, {1, 2, 1}, 1]
(*{4,6}*)
 ...

- asked by Wjx (18 votes), answered by WReach (25 votes)

—————————-

[How to debug the C code for LibraryLink?] http://mathematica.stackexchange.com/questions/119053/how-to-debug-the-c-code-for-librarylink

Recently, I use the C to rewrite a Mathematica function NonzeroBasis[], please see here for fully descriptions.

Here, NonzeroBasis[i,p,u,U] calculates the values of ...

- asked by Shutao TANG (11 votes), answered by Szabolcs (16 votes)

—————————-

[Is it possible to attach a debugger to a dynamically linked library on the supported OS?] http://mathematica.stackexchange.com/questions/119083/is-it-possible-to-attach-a-debugger-to-a-dynamically-linked-library-on-the-suppo

Recently, I discovered that LibraryLink technique is a very useful tool to improve the performance of function. Firstly, I need to use LibraryLink template to write C/C++ program. Then compiling the ...

- asked by Shutao TANG (10 votes), answered by user21 (3 votes)

—————————-

[Nothing not behaving as expected?] http://mathematica.stackexchange.com/questions/119239/nothing-not-behaving-as-expected

I was thinking that Nothing was doing the same job as the vanishing sequence ##&amp;[].

Yet this exemple shows it doesnt.

Association[If[True,Nothing]] (*returns Association[Nothing]*)
 ...

- asked by faysou (10 votes), answered by Szabolcs (12 votes)

—————————-

[Random walk on a Sierpinski gasket] http://mathematica.stackexchange.com/questions/119036/random-walk-on-a-sierpinski-gasket

I am trying to simulate a random walk on a Sierpinski gasket. The best strategy i could come up with is to use Nearest point function to determine the next possible step of my walker. But this creates ...

- asked by FEARxxx (9 votes), answered by Wjx (11 votes)

================================== Greatest hits from previous weeks: ==================================

[Creating legends for plots with multiple lines?] http://mathematica.stackexchange.com/questions/4025/creating-legends-for-plots-with-multiple-lines

So I have a graph with multiple lists, for e.g.

data = {{1,2}, {3,4}, {3,5}, {2,3} . . .}


If I then do ListLinePlot[Table[{#1,Log[b,#2]}&amp;@@@data, {b,1,10,2}]] I have no way to generate a legend  ...

- asked by Eiyriou von Kauyf (58 votes), answered by Jens (88 votes)

—————————-

[How can this image (optical illusion) be created with Mathematica?] http://mathematica.stackexchange.com/questions/24148/how-can-this-image-optical-illusion-be-created-with-mathematica

I came across this image the other day:

and liked the sensation of it pulsing. I was wondering if anyone would know how to create something similar with Mathematica (without the Pink Floyd Dark ...

- asked by Mike Honeychurch (51 votes), answered by halirutan (65 votes)

================================== Can you answer these? ==================================

[Is pattern matching just systematic guessing and checking?] http://mathematica.stackexchange.com/questions/119394/is-pattern-matching-just-systematic-guessing-and-checking

How does the pattern matcher work?

how does it match this example?

f[3, h[4]] /. f[x_, z_[y_]] :&gt; {x, y, z}

My guess is that the pattern matcher collects all the names in the expression f[3, ...

- asked by John Conor Cosnett (3 votes)

—————————-

[How can I move he documentation to another location after install on Windows?] http://mathematica.stackexchange.com/questions/119503/how-can-i-move-he-documentation-to-another-location-after-install-on-windows

How can I move he documentation to another location after install on Windows?

I would like to move the documentation to another partition on my Windows filesystem. Michael Hale in chat recommended ...

- asked by jamesson (4 votes)

—————————-

[How to perform convolutions on this complicated pdf?] http://mathematica.stackexchange.com/questions/119034/how-to-perform-convolutions-on-this-complicated-pdf

For a known pdf f[x], I need to calculate integrals over the probability density of the sum of Log[f[x]] over independent samples:

           ∑n
Q [t,n] ≡ P(   Log [f[xi]] = t)
           i=1

Since the sample ...

- asked by Jerry Guern (2 votes)

65 Tuesday, June 21, 2016

==================================
Top new questions this week:
==================================

[3D  graphic of soccer ball] http://mathematica.stackexchange.com/questions/118604/3d-graphic-of-soccer-ball

How to make a soccer ball 3D  graphic?

The following image is from Wikipedia, Spherical polyhedron:

Truncated icosahedron (left) and standard soccer ball (right)

...

- asked by vito (23 votes), answered by Michael E2 (23 votes)

—————————-

[The character sequence ”
. d” triggers line break in strings] http://mathematica.stackexchange.com/questions/118801/the-character-sequence-d-triggers-line-break-in-strings

Bug introduced in 7.0 or earlier and persists through 10.4.1

Bug isn’t present in version 5.2

Update: Sjoerd pointed out that this happens with any string and it is not related to StringForm. Just ...

- asked by Szabolcs (14 votes), answered by Sjoerd C. de Vries (12 votes)

—————————-

[Inconsistent handling of Dynamic option values; intended, omission, or bug?] http://mathematica.stackexchange.com/questions/118646/inconsistent-handling-of-dynamic-option-values-intended-omission-or-bug

In answering Dynamic ClipPlanes calculated from current ViewPoint Kuba and I got into a brief exchange regarding how Option values wrapped in Dynamic should be handled. For background John Fultz ...

- asked by Mr.Wizard (14 votes)

—————————-

[How can I plot this spirally surface?] http://mathematica.stackexchange.com/questions/118887/how-can-i-plot-this-spirally-surface

I would like to plot a surface that looks something like this sand spiral.

But I really have no idea how. Ideally I would like to be able to express this as a function in cartesian coordinates. I’m ...

- asked by user41147 (12 votes), answered by Thies Heidecke (28 votes)

—————————-

[Any manual on cell grouping management?] http://mathematica.stackexchange.com/questions/118649/any-manual-on-cell-grouping-management

Recently I come back to the problem of cell grouping and performed extensive search on this site and on MathGroup archive for information on how to use the possible values of the CellGroupingRules ...

- asked by Alexey Popkov (12 votes)

—————————-

[How can Mathematica be used to create Images like these?] http://mathematica.stackexchange.com/questions/118992/how-can-mathematica-be-used-to-create-images-like-these

Here are two examples of artistic image interpolation using just black lines. The first link shows the desired result created by an artist and the second done with C#.

TRIANGULATION: ANGULAR ...

- asked by R Hall (11 votes), answered by MarcoB (10 votes)

—————————-

[How to implement custom NIntegrate integration strategies?] http://mathematica.stackexchange.com/questions/118920/how-to-implement-custom-nintegrate-integration-strategies

How can new integration strategies algorithms be used with NIntegrate?

This is a different type of extension than the extensions with new integration rules, as described in the answer for the ...

- asked by Anton Antonov (10 votes), answered by Anton Antonov (10 votes)

================================== Greatest hits from previous weeks: ==================================

[Fit image of mountain to gaussian] http://mathematica.stackexchange.com/questions/109946/fit-image-of-mountain-to-gaussian

I want to detect the edges of an image of a mountain and then fit that to a gaussian.

I am unsure about how to only get the mountain edge, rather than every single edge in the image.

How do I ...

- asked by olliepower (13 votes), answered by Dr. belisarius (14 votes)

—————————-

[How to find the position of elements in a list satisfying criteria] http://mathematica.stackexchange.com/questions/180/how-to-find-the-position-of-elements-in-a-list-satisfying-criteria

Say I have a list x={2,4,6,8,10} and I want to find out the positions of the elements that are greater than 7.

Select[x, #&gt;7&amp;] gives the elements themselves, and Position[x,8] gives the  ...

- asked by PeterR (32 votes), answered by J. M. (29 votes)

================================== Can you answer these? ==================================

[Softmax Regression Classification Algorithm] http://mathematica.stackexchange.com/questions/118958/softmax-regression-classification-algorithm

I’m following the Stanford Machine Learning course while simultaneously developing my Mathematica abilities. I’m having issues with my Softmax Classifier implementation (for ref, have a look at these ...

- asked by Frederik Brinck Jensen (4 votes)

—————————-

[Protected Variable Error with Workbench 3.0] http://mathematica.stackexchange.com/questions/118919/protected-variable-error-with-workbench-3-0

I have Wolfram Workbench 3.0, build 78, with Mathematica 10.4 as the front end. I am using Windows 10. I am trying to run a simple test source code test.m:

fun[x_] := x^2;

I have an empty notebook ...

- asked by S2167 (2 votes)

—————————-

[Putting the elements of a list inside another list] http://mathematica.stackexchange.com/questions/118837/putting-the-elements-of-a-list-inside-another-list

I have the list list1 = 1, 3, 4, 5, 6 and want to put the elements of this list inside a list of 0’s, list2 = 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, where each element of list1 will be in the ...

- asked by user41129 (1 vote)

66 Tuesday, June 14, 2016

==================================
Top new questions this week:
==================================

[Are you interested in a Wolfram Workbench Update?] http://mathematica.stackexchange.com/questions/118154/are-you-interested-in-a-wolfram-workbench-update

I also posted this on the Wolfram Community site (link below)

Last week I attended the Wolfram Tour (which was great). I asked whenever we could expect a new version of Workbench, as the current ...

- asked by Frank Martin (18 votes), answered by Anton Antonov (14 votes)

—————————-

[Is manual adjustment of AccuracyGoal and PrecisionGoal useless?] http://mathematica.stackexchange.com/questions/118249/is-manual-adjustment-of-accuracygoal-and-precisiongoal-useless

This is a problem confusing me for years.

AccuracyGoal and PrecisionGoal are two options that I never truly understand and, to be honest, always avoid touching. Let’s first look at the descriptions ...

- asked by xzczd (15 votes)

—————————-

[Can Mathematica recompose an image?] http://mathematica.stackexchange.com/questions/117892/can-mathematica-recompose-an-image

The OP in this post on superuser.com asks how to recompose an image; quoting:

I have a set of images, which are parts of a bigger image.

I would like the images to assembled as automated as ...

- asked by mattiav27 (15 votes), answered by C. E. (13 votes)

—————————-

[How to implement custom integration rules for use by NIntegrate] http://mathematica.stackexchange.com/questions/118324/how-to-implement-custom-integration-rules-for-use-by-nintegrate

How can NIntegrate be extended with custom implementation of integration rules?

This answer of the question ”Monte Carlo integration with random numbers generated from a Gaussian distribution” shows ...

- asked by Anton Antonov (14 votes), answered by Anton Antonov (15 votes)

—————————-

[Unexpected behavior of Sequence – using Sequence to delete parts of an expression] http://mathematica.stackexchange.com/questions/118108/unexpected-behavior-of-sequence-using-sequence-to-delete-parts-of-an-expressi

I thought that assigning Sequence[] to the part of an expression was an effective way to remove it. For example, the following code yields 2,3,4,5:

xx = Range[5]; xx[[1]] = Sequence[]; xx

Thus, I ...

- asked by Hector (10 votes), answered by Leonid Shifrin (6 votes)

—————————-

[Why NIntegrate is badly-behaved on J9(x)
 2  by default?] http://mathematica.stackexchange.com/questions/117888/why-nintegrate-is-badly-behaved-on-j-frac92x-by-default

A friend of mine showed me this example:

Plot[BesselJ[9/2, x], {x, 0, 1},
 PlotLabel -&gt; Style["The integrand seems to be simple", 14]]

Integrate[BesselJ[9/2, x], {x, 0, 1}] // N
(*  ...

- asked by xzczd (10 votes), answered by Anton Antonov (6 votes)

—————————-

[How do I insert OwnValues inside a held expression without evaluating it?] http://mathematica.stackexchange.com/questions/118030/how-do-i-insert-ownvalues-inside-a-held-expression-without-evaluating-it

Here is a very long and complicated expression, which we abbreviate as a. I store it using SetDelayed because I want to perform algebraic manipulations on it:

ClearAll[a];
a := 1 + 1

Here is a ...

- asked by QuantumDot (9 votes), answered by Kuba (9 votes)

================================== Greatest hits from previous weeks: ==================================

[Where can I find examples of good Mathematica programming practice?] http://mathematica.stackexchange.com/questions/18/where-can-i-find-examples-of-good-mathematica-programming-practice

I consider myself a pretty good Mathematica programmer, but I’m always looking out for ways to either improve my way of doing things in Mathematica, or to see if there’s something nifty that I haven’t ...

- asked by J. M. (419 votes), answered by faysou (377 votes)

—————————-

[++ is dangerous for C programmers] http://mathematica.stackexchange.com/questions/107619/is-dangerous-for-c-programmers

I noticed this fact, that may be misleading for programmers used to C language.

In Mathematica, if you have a function f[] and an array v, and you write

v[[ f[] ]]++

the function f is called ...

- asked by Giovanni Resta (32 votes), answered by Mr.Wizard (24 votes)

================================== Can you answer these? ==================================

[Solve and design ”water flow”] http://mathematica.stackexchange.com/questions/118183/solve-and-design-water-flow

In some strategy game I play, I’ll have to change the terrain to make the water flow in some specific way to fulfill my goal. The water flow changes with terrain so if I can change the terrain wisely ...

- asked by Wjx (5 votes)

—————————-

[Is there a way to figure out the ”upper limit” of my PC’s computational ability in Mathematica?] http://mathematica.stackexchange.com/questions/117852/is-there-a-way-to-figure-out-the-upper-limit-of-my-pcs-computational-ability

I am doing some simulations with Finite Element Analysis (FEA) and part of it is forming a mesh in 3D and then using NDSolveValue to solve a differential equation on that mesh.

For some meshes, my ...

- asked by YungHummmma (2 votes)

—————————-

[Numerical testing of Hardy’s inequality] http://mathematica.stackexchange.com/questions/118061/numerical-testing-of-hardys-inequality

I want to check the following Hardy’s most fundamental inequality by using Mathematica:

∑∞ ( An )p   (   p  )p ∞∑
     ---   <   -----      apn
n=1   n        p− 1   n=1
...

- asked by vito (2 votes)

67 Tuesday, June 7, 2016

==================================
Top new questions this week:
==================================

[Bug with MapAt, Span, and Association?] http://mathematica.stackexchange.com/questions/116561/bug-with-mapat-span-and-association

Bug introduced in 10.0 and persisting through 10.4.1 or later

Related to Mapping (Query) a function at multiple locations in nested data via All, Span, it seems to me that the behavior of MapAt ...

- asked by Mr.Wizard (19 votes)

—————————-

[Joining points into 3D surface] http://mathematica.stackexchange.com/questions/117736/joining-points-into-3d-surface

This seems like a simple problem, but I can’t find any questions like it here so I’m making a new one. Apologies if I missed one.