Chapter 4Year 2017

4.1 Tuesday, December 26, 2017

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Top new questions this week:
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[How fast is my ﬁdget spinner spinning? A sound experiment!] https://mathematica.stackexchange.com/questions/162303/how-fast-is-my-fidget-spinner-spinning-a-sound-experiment

I would like to measure how fast my 6-bladed ﬁdget spinner spins. To do so, after giving it a hard spin, I gently touch the spinner with a wooden stirring stick to create a buzzing sound which ...

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[Sub-packages and auto-completion] https://mathematica.stackexchange.com/questions/162386/sub-packages-and-auto-completion

Cross-posted on Wolfram Community

I have a Mathematica application that consists of two sub-packages, corresponding to the contexts foo‘ (foo.m) and foo‘b‘ (b.m). Some of the deﬁnitions in foo.m ...

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[Why does Cases not ﬁnd a match to the pattern using _. when n is a number other than 1?] https://mathematica.stackexchange.com/questions/162559/why-does-cases-not-find-a-match-to-the-pattern-using-n-when-n-is-a-number-oth

I am not good in patterns in Mathematica, and so can’t ﬁgure what I am doing wrong.

This example works, when the exponent is 1

ClearAll[y,x,n]
Cases[{( y[x]/x)^1}, (y[x]/x )^(n_.) :&gt; n]

But ...

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[How to make an Epilog moveable with drag and drop] https://mathematica.stackexchange.com/questions/162572/how-to-make-an-epilog-moveable-with-drag-and-drop

I would like to make an Epilog moveable. For example, the following code generates a Manipulate with a framed pane containing some notes. I would like the user to be able to move those notes anywhere ...

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[Map every second element of a list] https://mathematica.stackexchange.com/questions/162334/map-every-second-element-of-a-list

Colors = Import[
"d:\\bitbucket\\diversity\\data\\nlcd\\nlcd-colors.csv", "CSV"]
{{0., " 0.00000000000 0.00000000000 0.00000000000"}, {11.,
" 0.27843137255 0.41960784314  ...

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[Table of precedence values for all System‘ symbols] https://mathematica.stackexchange.com/questions/162474/table-of-precedence-values-for-all-system-symbols

Has anyone created a table listing the precedences for all symbols? Also, it would be nice if there were a function that for a given precedence value or interval, returned all the symbols with that ...

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[How to make a custom DynamicImage which support mouse wheel and show pixel value?] https://mathematica.stackexchange.com/questions/162311/how-to-make-a-custom-dynamicimage-which-support-mouse-wheel-and-show-pixel-value

The built-in DynamicImage just click the plus sign or minus sign to rescale the image. I have to say click is a not very good operation. Could we make the custom DynamicImage which support the mouse ...

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

[xkcd-style Plots] https://mathematica.stackexchange.com/questions/11350/xkcd-style-plots

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 ...

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[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}

What’s the ...

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

[How can I check that a graph is edge weighted, fast?] https://mathematica.stackexchange.com/questions/162391/how-can-i-check-that-a-graph-is-edge-weighted-fast

I need to check if a graph is edge-weighted while maintaining good performance.

This should be an easy task, but it is not. It is a good example of why it is so terribly frustrating to work with ...

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[contour of inside of a volume] https://mathematica.stackexchange.com/questions/162306/contour-of-inside-of-a-volume

I have the following volume:

RegionPlot3D[-j^2*y^2 + j*l &lt; 11, {l, 0, 10}, {j, 0, 10}, {y, 0, 1}]

However, I am not able to obtain a 2D graph from it (contour), which shows the region inside the ...

- asked by Darrin Cope (1 vote)

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[Finsler or Lagrange geometry package?] https://mathematica.stackexchange.com/questions/162489/finsler-or-lagrange-geometry-package

I was wondering if there exist any packages or examples of work on Finsler-Lagrange geometry. I need it to do symbolic calculations, as for example calculations of non-linear connection coeﬃcients, ...

- asked by Athis Startis (1 vote)

4.2 Tuesday, December 12, 2017

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Top new questions this week:
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[Why does Mathematica results diﬀer from C++ results within machine precision?] https://mathematica.stackexchange.com/questions/161716/why-does-mathematica-results-differ-from-c-results-within-machine-precision

I am trying to wrap my head around ﬂoating-point precision. Performing the following numeric operation:

275./6.*1.03692775514337

in Mathematica and C++ and taking the diﬀerence of the two results ...

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[Bug with Block & Lookup: Scope Variable Leak] https://mathematica.stackexchange.com/questions/161616/bug-with-block-lookup-scope-variable-leak

After debugging a large chunk of code, I could identify this MWE.

ClearAll@test
test[var_String]:= Block[{association},
association = &lt;|"x"-&gt; &lt;|"key01"-&gt; "ok"|&gt;|&gt;[var];
...

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[Why is "k" in the output of Sum[Log[k]/k^k, {k,1,Infinity}]?] https://mathematica.stackexchange.com/questions/161704/why-is-k-in-the-output-of-sumlogk-kk-k-1-infinity

NSum[Log[k]/k^k, {k,1,Infinity}, WorkingPrecision-&gt;50]
(* 0.219947267975228664843531307905860703797097130 *)

But

Sum[Log[k]/k^k, {k,1,Infinity}]
(* -(PolyLog^(1,0))[0,1/k] *)

What does "k" in  ...

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[Simulating molecular dynamics eﬃciently] https://mathematica.stackexchange.com/questions/161471/simulating-molecular-dynamics-efficiently

The following website oﬀers a very nice molecular dynamics simulation: http://physics.weber.edu/schroeder/md/. It is pretty neat and quite a few physical phenomena can be described from that small ...

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[Why is listable not an attribute of the Set function?] https://mathematica.stackexchange.com/questions/161428/why-is-listable-not-an-attribute-of-the-set-function

The following is a list of attributes for the Set function:

Attributes[Set]

HoldFirst, Protected, SequenceHold

Why is Listable not included?

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[How to improve quality of this Plot3D] https://mathematica.stackexchange.com/questions/161771/how-to-improve-quality-of-this-plot3d

I tried driving up PlotPoints and MaxRecursion but the intersections look weird, is there some other trick I can do?

plot = Plot3D @@ {Abs[Sqrt[x] + Sqrt[y]] /. {x -&gt; Sin[2 x],
y -&gt; Cos[2  ...


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[How can I tell Mathematica to interpret 0xﬀﬀ as a hexadecimal number?] https://mathematica.stackexchange.com/questions/161646/how-can-i-tell-mathematica-to-interpret-0xffff-as-a-hexadecimal-number

I am stuck. I would like Mathematica simply accept 0x as a preﬁx Operator for Hexadecimal Numbers. I know that 0x is interpreted as 0*x, so maybe this is just not possible. I am a programmer and am ...

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

[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 ...

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[How to create eﬀect like Van Gogh’s stroke brush?] https://mathematica.stackexchange.com/questions/39003/how-to-create-effect-like-van-goghs-stroke-brush

I need to apply Van Gogh’s stroke brush eﬀect to a random image

Take the following image as an example:

Thank you so much if you could help!

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

[How to export graphics to SVG in script executed through cron?] https://mathematica.stackexchange.com/questions/161756/how-to-export-graphics-to-svg-in-script-executed-through-cron

I have a Wolfram script that generates plots, and exports them by evaluating expressions of the form

Export["/path/to/some.svg", myPlot];

The script works as intended when I run it from the [Unix] ...

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[Is it possible to prevent LUDecompositon from pivoting?] https://mathematica.stackexchange.com/questions/161552/is-it-possible-to-prevent-ludecompositon-from-pivoting

By construction LUDecomposition performs LU-decomposition with pivoting, i.e. with row permutations (otherwise the decomposition may not exist). Is it possible to tell Mathematica not to use pivoting ...

- asked by faleichik (1 vote)

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[How Many of R’s Functionalities Are Available From Inside Mathematica?] https://mathematica.stackexchange.com/questions/161664/how-many-of-rs-functionalities-are-available-from-inside-mathematica

When R is linked to Mathematica, how many of its functionalities are available from inside of Mathematica?

4.3 Tuesday, December 5, 2017

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Top new questions this week:
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[Sharing small code snippets] https://mathematica.stackexchange.com/questions/161269/sharing-small-code-snippets

As part of my never-ending goal of getting Mathematica code to be as easily shared as python packages I was recently thinking about how to make code easy to share.

So what’s are some good ways to ...

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[InverseTotient[ ]?] https://mathematica.stackexchange.com/questions/160949/inversetotient

Maple has a function InverseTotient( c ), which returns all those natural numbers $$n$$ whose Euler totient function $$\phi ( n ) = c$$. Is there an equivalent inverse of EulerPhi[ ] in Mathematica? If ...

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[What are the counterparts in Wolfram to left and right division of a matrix in other programming language, e.g. Julia and MATLAB?] https://mathematica.stackexchange.com/questions/161301/what-are-the-counterparts-in-wolfram-to-left-and-right-division-of-a-matrix-in-o

Sometimes, to ﬁnd the inverse of a matrix is a labor-consuming task or even "disgusting", especially when the matrix is "ill". It is said, e.g. in Julia, that the left/right division operation is ...

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[How to perform Loop subdivision on a triangle mesh with Mathematica?] https://mathematica.stackexchange.com/questions/161331/how-to-perform-loop-subdivision-on-a-triangle-mesh-with-mathematica

Every now and then, the question pops up how a given geometric mesh (e.g. a MeshRegion) can be reﬁned to produce a i.) ﬁner and ii.) smoother mesh. For example, the following triangle mesh from the ...

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[How to speed up ‘RotationMatrix‘?] https://mathematica.stackexchange.com/questions/161230/how-to-speed-up-rotationmatrix

I frequently run into the situation that I have to apply RotationMatrix to a huge bunch of 3D vectors and angles for numerical computations. On the one hand, the syntax of RotationMatrix forces me to ...

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[How to create (Header + Main area + Settings pane) notebook layout] https://mathematica.stackexchange.com/questions/161203/how-to-create-header-main-area-settings-pane-notebook-layout

cross-posted in community.wolfram.com

The goal is something like in the picture below.

Basic? I dare you to try to implement it in a manageable, scalable and ﬂexible way.

Requirements:

The ...

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My understanding of the irective is that it should preserve the sizes of all elements in the expression. But when I try this:

m1 = Inset[MaTeX["\\sqrt{\\phantom{a^2}b}", Magnification -&gt;  ...

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

[Elegant operations on matrix rows and columns] https://mathematica.stackexchange.com/questions/3069/elegant-operations-on-matrix-rows-and-columns

Question

The Mathematica tutorial has a section ’Basic Matrix Operations’, describing operations like transpose, inverse and determinant. These operations all work on entire matrices. I am missing a ...

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[How to create eﬀect like Van Gogh’s stroke brush?] https://mathematica.stackexchange.com/questions/39003/how-to-create-effect-like-van-goghs-stroke-brush

I need to apply Van Gogh’s stroke brush eﬀect to a random image

Take the following image as an example:

Thank you so much if you could help!

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

[Is there any code formatting style reference?] https://mathematica.stackexchange.com/questions/161344/is-there-any-code-formatting-style-reference

Is there any code formatting style reference for Wolfram Language similar to https://www.python.org/dev/peps/pep-0008/ and https://google.github.io/styleguide/javaguide.html? I’m teaching some people ...

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[Plot spectrum Fourier Transform] https://mathematica.stackexchange.com/questions/161381/plot-spectrum-fourier-transform

i want to plot the spectrum of the following function. I hope that anybody is able to help me. I don’t know how to plot the dirac delta function. I tried it this way but it didnťt work so far. Thanks! ...

- asked by Luke (1 vote)

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[Wrapper for mathematica code with GUI] https://mathematica.stackexchange.com/questions/160966/wrapper-for-mathematica-code-with-gui

I have a code written in Mathematica. What I am trying to do is to write a wrapper (say using Python) that will take user input for the Mathematica code, run the code, and create output.

I do not ...

4.4 Tuesday, November 28, 2017

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Top new questions this week:
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[The fastest thing since sliced cubes?] https://mathematica.stackexchange.com/questions/160527/the-fastest-thing-since-sliced-cubes

I’ve fallen down a rabbit hole recently, and need a reality check.

Suppose you have an arbitrary unit vector, $$u \in \mathbf {R}^3$$, and you cut up the unit cube into slices orthogonal to $$u$$ with ...

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[Mathematica does not respect linearity of integral] https://mathematica.stackexchange.com/questions/160655/mathematica-does-not-respect-linearity-of-integral

I have the following issue, trying to evaluate an integral. Mathematica tells me

Integrate[x^2 (1 + x^2)^(1/2) + y + z, {x, y, z}  Sphere[{0, 0, 0}, 1]]

(* 1/2  (3 Sqrt[2] - Log[2 (2 + Sqrt[2])])  ...

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Given an arbitrary mesh region, how can I eﬃciently obtain the graph describing the adjacency structure of mesh cells?

For example, given the following mesh,

SeedRandom[123]
pts = RandomReal[1,  ...

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[Can a symbol have both OwnValues and DownValues?] https://mathematica.stackexchange.com/questions/160740/can-a-symbol-have-both-ownvalues-and-downvalues

Mathematica Version 11.2 desktop / Windows 10 Pro 64-bit

I am trying to understand if a symbol can have both OwnValues and DownValues.

Is this acceptable or not acceptable?

As an experiment, I ...

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[Diﬀerences between DSolve and NDSolve] https://mathematica.stackexchange.com/questions/160560/differences-between-dsolve-and-ndsolve

I have a question about the diﬀerence in the solution between DSolve and NDSolve.

I want to solve the Friedmann equation of

\begin {align} 3\left (\frac {\dot {a}^2}{a^2}+\frac {k}{a^2}\right )=8\pi \end {align}

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[How to check if a vector is an eigenvector of a matrix using mathematica?] https://mathematica.stackexchange.com/questions/160801/how-to-check-if-a-vector-is-an-eigenvector-of-a-matrix-using-mathematica

Here is a vector

$\begin {pmatrix}i\\7i\\-2\end {pmatrix}$

Here is a matrix

$$\begin{pmatrix}2&amp; i&amp;0\\-i&amp;1&amp;1\\0 &amp;1&amp;0\end{pmatrix}$$

Is there a simple way to determine ...

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[How do I read values from photocells connected to analog pins of Arduino Uno?] https://mathematica.stackexchange.com/questions/160761/how-do-i-read-values-from-photocells-connected-to-analog-pins-of-arduino-uno

Generally, I need to connect my Arduino Uno to Mathematica and read 3 analog values from A0, A1, A2 in real-time.

As I understand, I have 2 ways of connecting Arduino to Mathematica:

First: I have a ...

================================== 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 ...

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[How to ﬁnd the position of elements in a list satisfying criteria] https://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  ...

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

[Default options of LinearSolve] https://mathematica.stackexchange.com/questions/160693/default-options-of-linearsolve

I would like to know what is the default options of LinearSolve when using LinearSolve[A,b], where A is a sparse matrix. There are several methods available such as Cholesky and Krysol etc., see here. ...

- asked by Wilhelm (1 vote)

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[Prevent Semi-Transparent Pixels in Export] https://mathematica.stackexchange.com/questions/160578/prevent-semi-transparent-pixels-in-export

I’ve noticed that when I export plots in Mathematica without a background, a lot of the text ends being made of semi-transparent pixels. For example:

myplot = ContourPlot[Cos[x] + Cos[y], x, 0, 4 ...

- asked by ereHsaWyhsipS (1 vote)

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[Identifying the range of the voice] https://mathematica.stackexchange.com/questions/160731/identifying-the-range-of-the-voice

I’m trying to do an equalization in an audio program called Audition.

To have a good voice equalization, I need to have a frequency range of my voice.

A minimum value and a maximum frequency value.

...

4.5 Tuesday, November 21, 2017

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Top new questions this week:
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[Is it possible to construct a fullform trace function] https://mathematica.stackexchange.com/questions/160184/is-it-possible-to-construct-a-fullform-trace-function

Is it possible to construct a FullFormTrace function that takes an arbitrary expression and prints a sequence (or returns a list) of the evaluation steps in full form. For instance

...

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[Integrate gives wrong result for simple function] https://mathematica.stackexchange.com/questions/160278/integrate-gives-wrong-result-for-simple-function

(probably) Bug introduced in 9.0 or earlier and persisting through 11.2

It looks like this.

NIntegrate[1/(2 + Sin[x + y]), {x, 0, 2 Pi}, {y, 0, 2 Pi}]
22.7929
Integrate[1/(2 + Sin[x + y]), {x, 0,  ...

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[Select the same elements from lists] https://mathematica.stackexchange.com/questions/160222/select-the-same-elements-from-lists

I need a special intersectant operation for List other than Set.

There maybe some duplicate elements, also need to count instead of merging as Intersection.

For example:

...

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[Building a convenient package distribution system] https://mathematica.stackexchange.com/questions/160330/building-a-convenient-package-distribution-system

The PacletManager is nice, but it’s not really a low-eﬀort system to work with.

Installing a package can be made pretty easy, but only if the location from which it is to be installed makes it so.

...

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[How to merge two lists with diﬀerent dimensions] https://mathematica.stackexchange.com/questions/160159/how-to-merge-two-lists-with-different-dimensions

I have two list, just like

a={a1,a2,a3,a4};
b={b1,b2,b3,b4,b5};

I want merge them and save to excel, as they have diﬀerent dimention, so I want it have the following format.

...

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[What is the elegant way of applying function to two lists?] https://mathematica.stackexchange.com/questions/160028/what-is-the-elegant-way-of-applying-function-to-two-lists

I am interested in ﬁnding the most concise elegant way of doing the following: We have a function fun[x1,x2] and two lists:

ls1={a1,a2,a3,a4,......}

and

ls2={b1,b2,b3,b4,......}

I ...

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[Legend displaying the expected number of points per unit area next to density plot] https://mathematica.stackexchange.com/questions/160193/legend-displaying-the-expected-number-of-points-per-unit-area-next-to-density-pl

I have 2d points and want to show a colored density plot of them. I also want to display a legend showing which point density (number of points per unit area) the colors in the plot represent.

Let’s ...

================================== 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  ...

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[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  ...

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

[Convergent inﬁnite sum fails to converge in Sum[...]] https://mathematica.stackexchange.com/questions/160280/convergent-infinite-sum-fails-to-converge-in-sum

It looks like this.

Limit[Sum[1/((2 n + 1) Pi I - x), {n, -m, m}], m -&gt; ]
= -(1/2) Tanh[x/2]

Sum[1/((2 n + 1) Pi I - x), {n, -, }]
Sum::div: Sum does not converge.

Turning on Regularization ...

- asked by huotuichang (1 vote)

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[Stacked BarChart with Callout] https://mathematica.stackexchange.com/questions/159945/stacked-barchart-with-callout

BarChart examples include this code :

BarChart[Table[Callout[RandomReal[{0, 1}], Unique["text"]], 2, 8],
BarSpacing -&gt; 2, ChartLayout -&gt; "Stacked"]

Its result should be :

But I can’t ...

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A similar post was found here, but it’s not using MMA.

A small test to export HDF5 ﬁle,

Export["test.h5", { "summary_Shoe" -&gt; anssummary, "summary_Tie" -&gt; anssummaryTie}]

Woks ﬁne.

But ...

4.6 Tuesday, November 14, 2017

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

[Drawing Cliﬀord Attractors in Mathematica] https://mathematica.stackexchange.com/questions/159668/drawing-clifford-attractors-in-mathematica

I came upon the "Cliﬀord Attractor" today, which are equations of the form: $x_{n+1}=\sin (a\ y_n) + c \cos (x_n)$ $y_{n+1}=\sin (b\ x_n) + d \cos (y_n)$

They create some incredible images by ...

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[Mismatch between Mathematica and COMSOL in 3D FEM problem] https://mathematica.stackexchange.com/questions/159506/mismatch-between-mathematica-and-comsol-in-3d-fem-problem

I would like to solve an advection-diﬀusion problem on a torus domain. There are three Dirichlet conditions: One at the inlet (concentration $$c=0$$), one at the outlet ($$c=0.5$$) and one at the wall ...

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[Unexpected behaviors in built-in functions] https://mathematica.stackexchange.com/questions/159895/unexpected-behaviors-in-built-in-functions

Existence of this topic is discussed in this mathematica.meta post.

I’m sure I am not the only non-beginner in WL who from time to time ﬁnds themselves not being able to predict an outcome of a ...

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[How to create a faded image using an existing image ﬁle] https://mathematica.stackexchange.com/questions/159662/how-to-create-a-faded-image-using-an-existing-image-file

The question is simple:

How can I take an image of a perfect stamp (load an image ﬁle) such as

and make it look old, worn, and faded, with missing arbitrary small bits, like the following stamp

...

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[Building a Noisy Function] https://mathematica.stackexchange.com/questions/159614/building-a-noisy-function

Here’s a nice function with a nice plot:

f[t_] := Exp[-Abs[t]] Sin[t];
Plot[f[t], {t, -10, 10}, PlotRange -&gt; All]

What I would like to do is to make it noisy... to add something to f[t] so ...

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[Inaccurate (non-smooth) boundary of the mesh generated by ToElementMesh] https://mathematica.stackexchange.com/questions/159775/inaccurate-non-smooth-boundary-of-the-mesh-generated-by-toelementmesh

I try to generate a mesh over a region, which has a wavy boundary at its bottom and needs very ﬁne mesh around the bottom.

However, the generated mesh boundary is not as smooth as the speciﬁed one. ...

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[remove transparency of background Image] https://mathematica.stackexchange.com/questions/159837/remove-transparency-of-background-image

I have the following image:

As you can see the background is kind of white-ish. Now my question is: How can I remove this transperancy of the background image ?

================================== 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 ...

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[Diﬀerence between != and =!=] https://mathematica.stackexchange.com/questions/153694/difference-between-and

I (think I) understand the diﬀerence between == (semantic) and === (syntactic). So when comparing != and =!= I was expecting a similar diﬀerence. So can anyone explain why the third line in this ...

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

[On comparable hardware, is Mathematica known to perform better in one operating system over the others?] https://mathematica.stackexchange.com/questions/159699/on-comparable-hardware-is-mathematica-known-to-perform-better-in-one-operating

Have any benchmarks been published by Wolfram Research to compare the performance of Mathematica in the major operating systems (Windows 10, Linux, MacOS)? If not, has anyone here performed such ...

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I am currently working with rainfall data from hurricane Harvey in order to better understand how to allocate resources in the event of another disaster. I want to accomplish a few things given this ...

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[how to count or extract Cases out of list of association that matches pattern] https://mathematica.stackexchange.com/questions/159783/how-to-count-or-extract-cases-out-of-list-of-association-that-matches-pattern

I have list of associations

lr1 = {&lt;|a -&gt; {0,0}, b -&gt; "TRUE"|&gt;, &lt;|b -&gt; "FALSE", a -&gt; {0,1}|&gt;, &lt;|a -&gt; {1,0}, b -&gt; "FALSE"|&gt;, &lt;|b -&gt; "TRUE", a -&gt;  ...

4.7 Tuesday, November 7, 2017

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

[Automatic edX Pdf Handout creator] https://mathematica.stackexchange.com/questions/159065/automatic-edx-pdf-handout-creator

I am trying to make an automatic handout creator for my courses on edX. It took me a long time to do it...

(If you don’t know edX: https://www.edx.org/

I wrote a program that adds to each slide ...

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[The area of a unit disk is $$2\pi$$? (NIntegrate over a numerical region)] https://mathematica.stackexchange.com/questions/159194/the-area-of-a-unit-disk-is-2-pi-nintegrate-over-a-numerical-region

EDIT: The example below concerns the construction of a numerical region from a general boolean-valued function. The question of how to properly construct such a region has been answered below (by M. ...

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[How many Capitals are closer to me than my own?] https://mathematica.stackexchange.com/questions/159041/how-many-capitals-are-closer-to-me-than-my-own

A recent question in chat about "When you are in Aachen, Germany, ﬁve other countries capitals are closer than Berlin." triggered me to try to write something to ﬁnd the cities automatically for ...

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[How to SortBy Last and in Reverse order?] https://mathematica.stackexchange.com/questions/159295/how-to-sortby-last-and-in-reverse-order

I am looking at the two functions SortBy and ReverseSort.

SortBy[{{1, 2, 3}, {2, 3, 1}, {3, 1, 2}, {2, 2}}, Last]

{{2, 3, 1}, {2, 2}, {3, 1, 2}, {1, 2, 3}}


How do I sort this by the ...

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[CatalanNumber[-1] formula on functions.wolfram.com unequals result from Mathematica] https://mathematica.stackexchange.com/questions/159143/catalannumber-1-formula-on-functions-wolfram-com-unequals-result-from-mathemat

The formula for CatalanNumber[-1] on this functions.wolfram.com page gives:

-(1/2)

whereas CatalanNumber[-1] directly evaluated gives?

-1

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[DiscretizeGraphics issues with transformations] https://mathematica.stackexchange.com/questions/159035/discretizegraphics-issues-with-transformations

I noticed DiscretizeGraphics does not work correctly with transformed Graphics such as

Graphics[Rotate[Rectangle[], 30ř]]

Both using Rotate and GeometricTransformation together with ...

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[How to locate a stream line starting from a saddle point?] https://mathematica.stackexchange.com/questions/159093/how-to-locate-a-stream-line-starting-from-a-saddle-point

I read in a table of gradient vectors and plot using the ListStreamPlot. I want to locate and color the line that represents the "boundary" of the ﬂux. A ﬂux line that 1)starts from a saddle point ...

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

[What are the most common pitfalls awaiting new users?] https://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 ...

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[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 ...

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

[Editing pdf ﬁles with Mathematica] https://mathematica.stackexchange.com/questions/159074/editing-pdf-files-with-mathematica

As an example, consider this pdf ﬁle.

Would it be possible to edit the pdf, such as removing a logo, the page numbering and even frames, and save the result as a pdf? I would like to keep the pdf ...

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[A question concerning a generalization of HypergeometricPFQ] https://mathematica.stackexchange.com/questions/159242/a-question-concerning-a-generalization-of-hypergeometricpfq

I have been trying to ﬁnd explicit formulas for the real and imaginary parts of the Wolfram function EllipticK. An interesting formula for the real part of EllipticK evaluated at a complex number is ...

- asked by John M. Campbell (1 vote)

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[Export cdf does not work in MathKernel command line] https://mathematica.stackexchange.com/questions/159210/export-cdf-does-not-work-in-mathkernel-command-line

I am using Mathematica through command line MathKernel. I am not trying to draw any graphics in the console. But I should be able to export things a CDF. Why can’t I export a CDF through command line ...

4.8 Tuesday, October 31, 2017

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

[Implementing a planetary terrain generation algorithm] https://mathematica.stackexchange.com/questions/158843/implementing-a-planetary-terrain-generation-algorithm

From this (now deleted) question I found this site where the author discusses a simple technique for random terrain generation on a sphere.

The method discussed is as follows:

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[Performance of Select] https://mathematica.stackexchange.com/questions/158583/performance-of-select

I have a data set of about 4*10^6 3d-coordinates.

From this volume I am sequentially selecting coordinates along one axis and manipulating this subset.

My question: can the Select function be ...

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[Create a simple split tree] https://mathematica.stackexchange.com/questions/158858/create-a-simple-split-tree

I am trying to create a simple split tree.

The growth should be only upwards, the vertical element length constant (1), the size of the horizontal bars should be halved in each iteration and the ...

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[Easy printing of executable code] https://mathematica.stackexchange.com/questions/158901/easy-printing-of-executable-code

I’m working on a package that has functions that call other existing and packaged functions. I’d like a way to output what some of those key calls are, so users can see what’s happening under the ...

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[Two bouncing balls in 1 dimension, issues with two diﬀerent methods?] https://mathematica.stackexchange.com/questions/158857/two-bouncing-balls-in-1-dimension-issues-with-two-different-methods

I’m trying to simulate 2 balls with the same mass and diameter bouncing one on top of another under gravity, see the illustration below (not ideal, but this is the best result I’ve got so far, the ...

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Is Mathematica able to communicate with macOS’s native Notiﬁcation Center in order to notify me if an evaluation ﬁnishes in any of my open notebooks?

I’m looking for a solution similar to this one ...

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[Why does repeated export of JPG-Images consume all memory?] https://mathematica.stackexchange.com/questions/158690/why-does-repeated-export-of-jpg-images-consume-all-memory

I was looking in the history of asked questions for similar questions, but none of the alike questions answered my problem suﬃciently. So I ask nevertheless.

My system memory is leaked by simple ...

================================== 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 ...

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[Elegant operations on matrix rows and columns] https://mathematica.stackexchange.com/questions/3069/elegant-operations-on-matrix-rows-and-columns

Question

The Mathematica tutorial has a section ’Basic Matrix Operations’, describing operations like transpose, inverse and determinant. These operations all work on entire matrices. I am missing a ...

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

[Number Formatting Functions Do Not Evaluate with ExportString] https://mathematica.stackexchange.com/questions/158694/number-formatting-functions-do-not-evaluate-with-exportstring

I need to export in a particular text ﬁle format and tried NumberForm, PaddedForm, AccountingForm, and DecimalForm to see which would work best. To my surprise only NumberForm evaluates when ...

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[DSolve Throw::nocatch: Uncaught Throw[Failed,balancefail] returned to top level. error in 11.2] https://mathematica.stackexchange.com/questions/158817/dsolve-thrownocatch-uncaught-throwfailed-balancefail-returned-to-top-level Reported also to WRI. [CASE:3965533] I am in the process of updating Kamke diﬀerentional equations tests for 11.2 when encountered a new error I have not seen before on one of the Kamke ODE’s ... - asked by Nasser (3 votes) —————————- [Solve for several constants using a set of initial conditions] https://mathematica.stackexchange.com/questions/158783/solve-for-several-constants-using-a-set-of-initial-conditions I have a set of diﬀerential equations that I am trying to solve for chemical reaction rate constants. So far I can get DSolve to solve the ODEs with initial conditions which provides the chemical ... - asked by razzle_dazzle_84 (1 vote) 4.9 Tuesday, October 24, 2017 ================================== Top new questions this week: ================================== [Strange behavior of Table] https://mathematica.stackexchange.com/questions/158186/strange-behavior-of-table Whenever I run the code a = 0; code := (a++); Table[code; a, {1000}] I get a list of 1000 zeros. However, if I replace 1000 with 100, then a get a list equal to Range[100]. Is this a bug or am I ... - asked by Antonio De Juárez (12 votes), answered by Szabolcs (21 votes) —————————- [Large increase in integrate result leaf size after version 9. Looking for common cause] https://mathematica.stackexchange.com/questions/158059/large-increase-in-integrate-result-leaf-size-after-version-9-looking-for-common reported to WRI. [CASE:3960295] I run the CAS integration tests which contains 15000 integrals over number of Mathematica versions. I found that the average leaf size of the anti-derivatives ... - asked by Nasser (12 votes), answered by Itai Seggev (8 votes) —————————- [Convert Real packed array of pairs to Complex packed array] https://mathematica.stackexchange.com/questions/158082/convert-real-packed-array-of-pairs-to-complex-packed-array I have a Real packed array arr. It may have arbitrary depth but Last@Dimensions[arr] == 2. For example, arr = N@Partition[Partition[Range[24], {2}], 3] I want to convert it to a Complex packed ... - asked by Szabolcs (12 votes), answered by Carl Woll (9 votes) —————————- [Conversion of Matrix of Characters to a Matrix of Zeros and Ones based on Column Frequency] https://mathematica.stackexchange.com/questions/158465/conversion-of-matrix-of-characters-to-a-matrix-of-zeros-and-ones-based-on-column I have a matrix of characters that I wish to convert to a matrix of 0’ s and 1’ s. Although the matrix is large[17, 4301], I subsample this for purposes of my question. The matrix is:  m = {{"T", ... - asked by Stuart Poss (11 votes), answered by Nasser (4 votes) —————————- [What’s the fastest way to take Mean of a Tensor in given slot?] https://mathematica.stackexchange.com/questions/158345/whats-the-fastest-way-to-take-mean-of-a-tensor-in-given-slot One should expect that the implementation of the built-in function Mean was quick. However, as I recently observed, this is not true at all, in particular for matrices. Just compare Mean to the ... - asked by Henrik Schumacher (9 votes), answered by Carl Woll (6 votes) —————————- [Animating a Potential Function (eigenfunctions of Laplace’s equation)] https://mathematica.stackexchange.com/questions/158412/animating-a-potential-function-eigenfunctions-of-laplaces-equation I have written the following DynamicModule. The idea is that you can change the boundary, calculate the eigenfunctions and then animate them. Here is the code: DynamicModule[{pts, bdr = {{0, 0}, {1, ... - asked by Hugh (9 votes), answered by Kuba (8 votes) —————————- [How to implement a free version of WebImageSearch?] https://mathematica.stackexchange.com/questions/158134/how-to-implement-a-free-version-of-webimagesearch I really don’t like functions that I have to pay for, if they can be implemented for free. Is there a way to get around this pay-wall for WebImageSearch? Perhaps using some other free api or service? ... - asked by M.R. (9 votes), answered by b3m2a1 (11 votes) ================================== Greatest hits from previous weeks: ================================== [How to express trigonometric equation in terms of of given trigonometric function?] https://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 (27 votes), answered by Simon (34 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 (26 votes), answered by masterxilo (11 votes) ================================== Can you answer these? ================================== [How to draw a generic 3D closed shape to be analyzed in AceFEM?] https://mathematica.stackexchange.com/questions/158446/how-to-draw-a-generic-3d-closed-shape-to-be-analyzed-in-acefem I would like to draw a 3D shape to test my AceGen procedure. I will insert the AceFEM part of my code. In this example, I have performed the analysis on a hexahedron element. - asked by M.Rock (2 votes) —————————- [Kernel crash with KeySelect and repeated keys on list of rules] https://mathematica.stackexchange.com/questions/158421/kernel-crash-with-keyselect-and-repeated-keys-on-list-of-rules After running KeySelect[{"a" -&gt; 0, "a" -&gt; 1}, True &amp;] my kernel either hangs forever (possibly with the eventual warning that "the kernel is not responding to a Dynamic evaluation") or ... - asked by masterxilo (2 votes) —————————- [How to remove circled noise from image] https://mathematica.stackexchange.com/questions/158123/how-to-remove-circled-noise-from-image Consider a simpliﬁed example: noise noise = Table[ RandomVariate[ NormalDistribution[1, 0.2]] Sin[Sqrt[x^2 + y^2]]^8, {x, -16, 16 - 16/512, 32/512}, {y, -16, 16 - 16/512, 32/512}]; ... - asked by xslittlegrass (3 votes) 4.10 Tuesday, October 17, 2017 ================================== Top new questions this week: ================================== [Is building an event-based parser possible/reasonable in Mathematica (WL)?] https://mathematica.stackexchange.com/questions/157834/is-building-an-event-based-parser-possible-reasonable-in-mathematica-wl Too long? Go to Problems section Background I like to learn by doing small, sometimes artiﬁcial, projects. Among other things I had ’parsers’, and ’stream methods / streams in MMA’ on my to learn ... - asked by Kuba (11 votes) —————————- [Test if a list is a constant integer multiple of another list] https://mathematica.stackexchange.com/questions/157783/test-if-a-list-is-a-constant-integer-multiple-of-another-list I have a list of lists, and I want to eliminate all the lists that are constant integer multiples of another list. My initial approach was to divide the lists using nested tables. ex1 = {{1, 1, 1}, ... - asked by Lokdal (10 votes), answered by Mr.Wizard (9 votes) —————————- [Cannot Reproduce Answer to 99576] https://mathematica.stackexchange.com/questions/157889/cannot-reproduce-answer-to-99576 Bug introduced between versions 10.1 and 10.4, and persisting through 11.2. Reported to Wolfram, Inc as CASE:3958778. Using either 11.2 or 10.4 on Windows 10 (64 bit), I am unable to reproduce the ... - asked by bbgodfrey (9 votes) —————————- [Does ‘SeedRandom‘ give the same set of random numbers across operating systems?] https://mathematica.stackexchange.com/questions/157621/does-seedrandom-give-the-same-set-of-random-numbers-across-operating-systems If I use SeedRandom[12345] RandomReal[{0,1},100] I get the same random numbers on two versions of Mathematica: 10.4.1.0 on Windows 10 and 11.1.1.0 on Windows 7. But does the same seed get the ... - asked by JimB (9 votes), answered by halirutan (8 votes) —————————- [Fill the data of an Association based on a list] https://mathematica.stackexchange.com/questions/157852/fill-the-data-of-an-association-based-on-a-list Consider the following the list and association. list1 = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; asc = &lt;|1 -&gt; a, 4 -&gt; b, 7 -&gt; c, 10 -&gt; d|&gt;; I would like to create an association which ... - asked by Anjan Kumar (7 votes), answered by Kuba (5 votes) —————————- [How to extract data points from two graphics and ﬁnd the intersections between them?] https://mathematica.stackexchange.com/questions/157787/how-to-extract-data-points-from-two-graphics-and-find-the-intersections-between I am working on a mathematical problem called "Buﬀon’s Needle". Here is the setup I made: point[v_, u_] := Normalize[v - u] + u experiment50 = Show[ Graphics[ Table[{ RGBColor[0, 0, 0], ... - asked by Anna Morales Melgares (7 votes), answered by kglr (7 votes) —————————- [How to thread over ragged list while skipping empty sub-lists?] https://mathematica.stackexchange.com/questions/157635/how-to-thread-over-ragged-list-while-skipping-empty-sub-lists I have a very large ragged list result that is a list of list of pairs where sometimes the sub-list contains the empty list. res = {{{20, 1}, {200, 2}}, {{}}, {{175, 1}}}; In the above minimal ... - asked by Edmund (7 votes), answered by kglr (9 votes) ================================== Greatest hits from previous weeks: ================================== [LaTeXand Mathematica] https://mathematica.stackexchange.com/questions/736/latex-and-mathematica I quite often would like to draw graphics in my LaTeXdocuments using Mathematica. I have encountered three problems. I would like to know if there are any workarounds to these problems I would ... - asked by Thomas Rot (108 votes), answered by Simon (40 votes) —————————- [Code that generates a mandala] https://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 (48 votes), answered by Anton Antonov (71 votes) ================================== Can you answer these? ================================== [Export BatchNormalizationLayer as MXNet] https://mathematica.stackexchange.com/questions/157856/export-batchnormalizationlayer-as-mxnet I just tried to import a net from mathemtica into pythons using MXNet. It works ﬁne with the following manual. However, as soon as I try to add a BatchNormalizationLayer to my net MXNets bind() ... - asked by MaxJ (3 votes) —————————- [ListPlot point colors by list of colorfunctions] https://mathematica.stackexchange.com/questions/157963/listplot-point-colors-by-list-of-colorfunctions I would like to display the positions of a collection of particles as a function of time (animated) and color code them based on their velocities. For example, consider 10 particles moving in a 2D ... - asked by SeanM (1 vote) —————————- [Why are Label Pixelated?] https://mathematica.stackexchange.com/questions/157693/why-are-label-pixelated It seems that Mathematica implements the processing of labels quite diﬀerent for diﬀerent plot-functions. The good -> Plot[]: l1 = GraphPlot[Table[i -&gt; 1, {i, 0, 1}]] TPlot = Plot[{Cos[x], ... - asked by Freeman (2 votes) 4.11 Tuesday, October 10, 2017 ================================== Top new questions this week: ================================== [How can I determine the type of a packed array?] https://mathematica.stackexchange.com/questions/157484/how-can-i-determine-the-type-of-a-packed-array Packed arrays can be of type Integer, Real or Complex. Knowing that an array arr is packed, how can I eﬃciently determine its type? - asked by Szabolcs (15 votes), answered by Szabolcs (17 votes) —————————- [Deleting sublists from lists] https://mathematica.stackexchange.com/questions/157267/deleting-sublists-from-lists I have a list consisting of symbols and integers. I would like to delete the integers from the list only if a symbol precedes and follows each integer: testList={a,b,3,c,4,5,d,e,f,1,g,4} becomes: ... - asked by Suite401 (12 votes), answered by jjc385 (13 votes) —————————- [Summation bug in 11.2] https://mathematica.stackexchange.com/questions/157290/summation-bug-in-11-2 If I sum all the positive-numbered Fourier coeﬃcients of $$\cos (x)$$, I get the correct answer. If I sum the negative-numbered ones, I get a wrong answer. Splitting the sum into two parts somehow ... - asked by level1807 (10 votes), answered by Michael E2 (14 votes) —————————- [Calculating the size of objects in the picture] https://mathematica.stackexchange.com/questions/157374/calculating-the-size-of-objects-in-the-picture I’m new to Wolfram Mathematica. I have an initial image: My goal is to ﬁnd a radius of the water drop, like so: With that in mind, I’ve changed the initial photo: resultImage = ... - asked by Elias (9 votes), answered by b3m2a1 (7 votes) —————————- [Overlapping graphic primitives] https://mathematica.stackexchange.com/questions/157489/overlapping-graphic-primitives I am trying to make a ﬁgure in Mathematica using some graphic primitives: rod[l_, r_] := GraphicsGroup[{Opacity[.1], {Disk[{-l/2 + r, 0}, r, {$Pi]/2 , 3 \[Pi]/2}]}, {Disk[{l/2 - r, 0}, r, ... - asked by Ruud3.1415 (7 votes), answered by kglr (3 votes) —————————- [How can I implement my own documentation search function?] https://mathematica.stackexchange.com/questions/157303/how-can-i-implement-my-own-documentation-search-function The current documentation search doesn’t allow for very sophisticate searching, can I write my own function to search through the docs? - asked by b3m2a1 (7 votes), answered by b3m2a1 (8 votes) —————————- [Can I implement something like the old documentation help browser?] https://mathematica.stackexchange.com/questions/157317/can-i-implement-something-like-the-old-documentation-help-browser Old versions of Mathematica had a help browser that was more click through and structured. How can I reimplement something like that for the new (since v6) docs? - asked by b3m2a1 (6 votes), answered by b3m2a1 (10 votes) ================================== Greatest hits from previous weeks: ================================== [What are the most common pitfalls awaiting new users?] https://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 (405 votes), answered by Michael E2 (235 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 (58 votes), answered by Artes (56 votes) ================================== Can you answer these? ================================== [Memoization of built in function] https://mathematica.stackexchange.com/questions/157429/memoization-of-built-in-function What is the best way to let mathematica memoize built-in function like e.g. SphericalHarmonicY[l,m,th,ph] One possibility would be for sure: sphericalHarmonicY[l_,m_,th_,ph_]:= ... - asked by Mr Puh (3 votes) —————————- [Can’t import Gluon into mma] https://mathematica.stackexchange.com/questions/157466/cant-import-gluon-into-mma This is a simple DNN from Fast, portable neural networks with Gluon HybridBlocks: This is json ﬁle and params ﬁle of Gluon(MXNet) import mxnet as mx from mxnet.gluon import nn print("mxnet ... - asked by partida (4 votes) —————————- [NIntegrate and deﬁnite Integrate give diﬀerent results] https://mathematica.stackexchange.com/questions/157300/nintegrate-and-definite-integrate-give-different-results Suppose the function f[x_,q_]=(15876 Exp[-0.527076 q^2] (x^2-2 x+2) SphericalBesselJ[1,5 q]^2 (q^2-8100 x^2))/(3425*Pi*q^5*x); I need to perform the integration over q in the domain ... - asked by John Taylor (1 vote) 4.12 Tuesday, October 3, 2017 ================================== Top new questions this week: ================================== [Frown for a sex change, or, how do I unbork the "FacialGender" classiﬁer in 11.2?] https://mathematica.stackexchange.com/questions/156847/frown-for-a-sex-change-or-how-do-i-unbork-the-facialgender-classifier-in-11 The limits of machine learning. I thought the new "FacialGender" option for Classiﬁer would be an amusing thing to explore. So far, so good. But that’s me with bed-head. So let’s try a picture ... - asked by Verbeia (17 votes), answered by Searke (2 votes) —————————- [Improve the mesh smoothing procedure] https://mathematica.stackexchange.com/questions/156611/improve-the-mesh-smoothing-procedure My question is inspired by this answer about meshing with quadrilateral elements. The following functions are my (naive) try of implementing the Laplacian smoothing. I ﬁnd interior nodes in the mesh ... - asked by Pinti (11 votes), answered by user21 (10 votes) —————————- [Possible bug in RegionUnion or related functions?] https://mathematica.stackexchange.com/questions/157031/possible-bug-in-regionunion-or-related-functions Functions for derived geometric regions (RegionUnion and related) have been signiﬁcantly updated in MMA 11.2 and now this simple example doesn’t work any more as expected. Could this be a bug or I am ... - asked by Pinti (8 votes), answered by Szabolcs (5 votes) —————————- [Dataset - append row with a value which depends on two other rows] https://mathematica.stackexchange.com/questions/156980/dataset-append-row-with-a-value-which-depends-on-two-other-rows I have go through the forum but did not see this question. Hope I don’t miss it. I want to add a new colum "C" to a dataset with existing columns named "A" and "B". The value of "C" shall be the ... - asked by Porty (7 votes), answered by WReach (6 votes) —————————- [How to tell Mathematica to do this with decimal part of real number?] https://mathematica.stackexchange.com/questions/156823/how-to-tell-mathematica-to-do-this-with-decimal-part-of-real-number My apologies if this was asked here before. My friend and I want to do this: Suppose that we have some real number $$a. a_1 a_2...a_n...$$ where $$a_i$$ are digits in the set $$\{1,2,3,4,5,6,7,8,9,0\}$$ ... - asked by Antoine de Paladin (7 votes), answered by Edmund (6 votes) —————————- [FullForm of b/c and c/b with diﬀerent order] https://mathematica.stackexchange.com/questions/156757/fullform-of-b-c-and-c-b-with-different-order I am studying Mathematica myself and doing some exercises for improvement.  Question: Try to guess the internal forms of b/c and c/b. Verify your answer using FullForm. Here is what I got by ... - asked by anhnha (7 votes), answered by Mr.Wizard (6 votes) —————————- [Generate random walk on a graph] https://mathematica.stackexchange.com/questions/156626/generate-random-walk-on-a-graph I have a graph with 100 nodes and 200 edges. How can I generate a random walk in it and animate it? - asked by nasha amalina (7 votes), answered by rhermans (13 votes) ================================== Greatest hits from previous weeks: ================================== [How to ﬁnd the position of elements in a list satisfying criteria] https://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 (47 votes), answered by J. M. (45 votes) —————————- [How to calculate contour integrals with Mathematica?] https://mathematica.stackexchange.com/questions/34073/how-to-calculate-contour-integrals-with-mathematica How to calculate the integral of $$\frac {1}{\sqrt {4 z^2 + 4 z + 3}}$$ over the unit circle counterclockwise for each branch of the integrand? - asked by user64494 (30 votes), answered by Artes (53 votes) ================================== Can you answer these? ================================== [How to decode Ascii85 format (AKA base85)?] https://mathematica.stackexchange.com/questions/156667/how-to-decode-ascii85-format-aka-base85 The ASCII85 encoding is a binary string encoding where every four bytes are encoded with ﬁve ASCII letters, using 85 diﬀerent types of characters. Unfortunately, it’s not in CharacterEncodings: ... - asked by M.R. (2 votes) —————————- [FIR ﬁlter and the relation between Sample rate and cut-oﬀ frequency] https://mathematica.stackexchange.com/questions/156685/fir-filter-and-the-relation-between-sample-rate-and-cut-off-frequency I have problem to unterstand the logic of the cut-oﬀ frequency of the FIR ﬁlter. Suppose my sample rate is 2MHz and I want to design a lowpass ﬁlter with a cut-oﬀ frequency 100Hz. What will be ... - asked by shabir barzanjeh (2 votes) —————————- [FindCluster only ﬁnds cluster "with a little help"] https://mathematica.stackexchange.com/questions/156984/findcluster-only-finds-cluster-with-a-little-help Currently I made some slides to illustrate clustering. As an example I made a point set of two clusters:  {clusters, graph} = Block[{c1, c2, cluster1, cluster2}, c1 = {1, 2}; cluster1 = (# + ... - asked by mgamer (4 votes) 4.13 Tuesday, September 26, 2017 ================================== Top new questions this week: ================================== [Finite element mesh not resolving features] https://mathematica.stackexchange.com/questions/156174/finite-element-mesh-not-resolving-features I am trying to make a ﬁnite element mesh in 2D. The features are not found by ToElementMesh. This is a shelf bracket with nails. I build the region using RegionDiﬀerence and RegionUnion and the ... - asked by Hugh (11 votes), answered by Young (9 votes) —————————- [Are the mail settings as given in preferences still programmatically accessible in V 11.2] https://mathematica.stackexchange.com/questions/156183/are-the-mail-settings-as-given-in-preferences-still-programmatically-accessible In versions before 11.2 (and after 9) one could get the current settings as defined in the preferences (Internet &amp; Email -> Mail Settings) with Options[SendMail]. As the options for SendMail have ... - asked by Albert Retey (11 votes), answered by rhermans (9 votes) —————————- [Implement fractional Laplacian] https://mathematica.stackexchange.com/questions/156420/implement-fractional-laplacian What is a way to implement the Fractional Laplacian with Mathematica? How can we apply such implementation to numerically solve the problem (-\Delta)^su = 1 \text{ in } B_1(0), \\ u = 0 \text{ in ... - asked by Jay (9 votes), answered by Henrik Schumacher (14 votes) —————————- [Blur, GaussianFilter and ImageConvolve doesn’t work on some images] https://mathematica.stackexchange.com/questions/156210/blur-gaussianfilter-and-imageconvolve-doesnt-work-on-some-images In versions 8.0.4 and 9.0.1 applying Blur to an image gives expected result: img = Import["http://i.stack.imgur.com/UsJTa.png"] blurred = Blur[img, 5] ColorSeparate[blurred] But ... - asked by Alexey Popkov (9 votes), answered by Alexey Popkov (11 votes) —————————- [Error and uncertainty propagation: Is using Precision/Accuracy a sound strategy?] https://mathematica.stackexchange.com/questions/156481/error-and-uncertainty-propagation-is-using-precision-accuracy-a-sound-strategy Questions What are the available resources to deal with experimental error and uncertainty propagation in Mathematica? Given that Mathematica already uses linearized model of error propagation on ... - asked by rhermans (8 votes) —————————- [Unexpected behavior using ‘ReplaceAll[]‘ for nested lists] https://mathematica.stackexchange.com/questions/156538/unexpected-behavior-using-replaceall-for-nested-lists ReplaceAll[] might lead to unexpected behavior (at least it surprised me). I use ReplaceAll[] to convert a list (basically data cleanup). For the command: {{1, "2"}, {2, "3"}} /. {x_, _ } :&gt; {x, ... - asked by Dennis (7 votes), answered by Szabolcs (9 votes) —————————- [What are the possible Method option values for plotting functions?] https://mathematica.stackexchange.com/questions/156475/what-are-the-possible-method-option-values-for-plotting-functions Many plotting functions have a Method options with descriptions like this: Plot: "the method to use for reﬁning curves" RegionPlot: "the method to use for reﬁning regions" ContourPlot: "the method ... - asked by Szabolcs (7 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 (46 votes), answered by Silvia (47 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? ================================== [Possible Symbolic Integration Bug] https://mathematica.stackexchange.com/questions/156215/possible-symbolic-integration-bug Bug introduced between 5 and 8 and persisting through 11.2 I think I may have found a bug, and want to verify is this reproducible in other versions and platforms and not a mistake of mine. I ... - asked by yyli (5 votes) —————————- [Finding the slowest decay to a value for a 2D function] https://mathematica.stackexchange.com/questions/156338/finding-the-slowest-decay-to-a-value-for-a-2d-function I have a function acf2[x,y] that describes the auto-correlation function of a simulated real surface, with a peak at the origin (acf2[0,0] = 1), and need to ﬁnd the maximum distance from the origin ... - asked by L.Todhunter (1 vote) —————————- [Can Mathematica run javascript on a website?] https://mathematica.stackexchange.com/questions/156377/can-mathematica-run-javascript-on-a-website One way of running Javascript on a website is to use for instance Greasemonkey. By any chance, would it be possible to execute Javascript commands from Mathematica? - asked by anderstood (1 vote) 4.14 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 $$D=\{z\in {\bf C}: |z|<1\}$$, and a domain $$D\setminus \overline {B_{1/2}(-1/2)}$$ where $$B_r(z_0)$$ 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) 4.15 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 I've 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 I've 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) 4.16 Tuesday, September 5, 2017 ================================== Top new questions this week: ================================== [Finding $$n^{\text {th}}$$ 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 $$n^{\text {th}}$$ 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 $$l \in L$$ it returns the index of the largest number $$s \in S$$ 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 $$m\times n$$ and $$k\times m$$ 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 $$\int _{0}^{1}\frac {x^{-1/2}}{e^{x}-1} \sin \left (\frac {1}{x}\right )dx$$] https://mathematica.stackexchange.com/questions/155066/strange-result-for-an-improper-integral-int-01-fracx-1-2ex-1-s The improper integral \[\int _{0}^{1}\frac {x^{-1/2}}{e^{x}-1} \sin \left (\frac {1}{x}\right )dx$ is convergent conditionally. (Applying Dirichlet Test, $\frac {x^{-1/2}}{e^{x}-1}$ ... - asked by user250236 (1 vote) —————————- [Perplexing simpliﬁcation of RotationMatrix] https://mathematica.stackexchange.com/questions/154793/perplexing-simplification-of-rotationmatrix The result of FullSimplify[RotationMatrix[, {Cos[], Sin[], 0}], &gt; 0].{0, 0, 1} in Mathematica 11 is {Sign[Sec[]]^2 Sin[] Sin[], -Cos[] Sin[], Cos[]} 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) 4.17 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) —————————- [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) —————————- [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: $\frac {F(x)}{F(1)} = 2F\left (\frac {(1+x)^2}{4a}\right )-F(x/a)$ 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 )/(1 - r^2 + 2 I r ) I try this, i doesn't work Assuming[{ &gt; 0, r &gt; 0}, ... - asked by Bendesarts (1 vote) 4.18 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) —————————- [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) —————————- [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 $\frac {\sum _{i=1}^n x(i)^2}{n}-\frac {\left (\sum _{i=1}^n x(i)\right ){}^2}{n^2}$ 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[, ], x]; 2[x1_, ... - asked by Glostas (1 vote) 4.19 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) —————————- [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) —————————- [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) 4.20 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) —————————- [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[], r Sin[], 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 $$h_m$$. \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) 4.21 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 $$\frac {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) 4.22 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. Let's 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) 4.23 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 + k t] and r == t Csc[] as t goes from -1 to 1. (n and k are constants, and y, r, and 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 APIpart 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) 4.24 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) 4.25 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) 4.26 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 $$10^n$$ and not e.g. as 1000 for $$n = 3$$ or the rational $$\frac {1}{1000}$$ 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 $\sum _{n=2}^{\infty } \frac {(-1)^n}{\sqrt {\log (n)}}$ 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) 4.27 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 $$\mathbb {Q}(\sqrt {2} + \sqrt {3})$$ can be represented by a $$4$$ - dimensional vector space over $$\mathbb {Q}$$ with basis $$\{1, \sqrt {2}, \sqrt {3}, \sqrt {6}\}$$. 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; = 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) 4.28 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; NDSolveFEM 1 = 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) 4.29 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 $$\left \{\left . T(c,d)\right |c,d\in \mathbb {Z}\right \}$$, 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. $$H'' + \frac {2}{r}H'-\frac {\partial V_{eff}(H,r)}{\partial H}=0$$ with the following conditions $$\frac {dH}{dr}(r=0)=0$$ and $$H(r= \infty )=0$$ Regardless of the ... - asked by Konstantinos (2 votes) 4.30 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 Can't use dynamic.It throws An unknown box name.
So if I want to  ...

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[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 ...

4.31 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:

...

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[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, ...

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[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 ...

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[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 ...

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[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  ...

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[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?

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[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

Module[{seg, areas, indexMaxarea, maxArea},
seg =  ...

================================== 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[], r Sin[], r^2}, {r, 0,  ...

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[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 ...

================================== 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,  ...

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[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:

Here is ...

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[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 ...

4.32 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 =  ...

—————————-

[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 ...

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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 ...

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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 ...

—————————-

[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

—————————-

[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 ...

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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 ...

================================== 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 ...

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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 ...

================================== 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}]]

—————————-

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 ...

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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?

4.33 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 ...

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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,  ...

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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 ...

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[Exchanging numpy arrays between Python and Mathematica?] https://mathematica.stackexchange.com/questions/144770/exchanging-numpy-arrays-between-python-and-mathematica

I've 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  ...

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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 ...

—————————-

[Where are my Cloud Credits going?] https://mathematica.stackexchange.com/questions/144859/where-are-my-cloud-credits-going

In less than a month I've 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  ...

—————————-

[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  ...

================================== 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 ...

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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". ...

================================== 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;
...

—————————-

[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}};
...

—————————-

[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 ...

4.34 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, ...

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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 ...

—————————-

[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?

—————————-

[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 ...

—————————-

[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 ...

—————————-

[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 ...

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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 ...

================================== 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 ...

—————————-

[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 ...

================================== 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 ...

—————————-

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  ...

—————————-

[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 ...

4.35 Tuesday, April 18, 2017

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

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 ...

—————————-

[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 ...

—————————-

[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

...

—————————-

[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, $$G(x_1,x_2,x_3,x_4)$$ to the very easy system of PDEs:

—————————-

[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 =  ...

—————————-

[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 ...

—————————-

[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 ...

================================== 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 ...

—————————-

[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___] :=  ...

================================== 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 ...

—————————-

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 =  ...

—————————-

[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 =
...


4.36 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"]
...

—————————-

[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 ...

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[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

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[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 = ...

—————————-

[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 ...

—————————-

[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.

4.50 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?

—————————-

[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 ...

—————————-

[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; /@  ...

—————————-

[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 ...

—————————-

[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 ...

—————————-

[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 ...

—————————-

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;  ...

================================== 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[], r Sin[], r^2}, {r, 0,  ...

—————————-

[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?

================================== 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 ...

—————————-

[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 $$\hat {f}$$, the Fourier transform of ...

Style[Plot3D[Cos[x + 0*y], {x, -10, 10}, {y, -2, 42}, Mesh -&gt; None],
Antialiasing -&gt; True]