## Chapter 5Year 2016

### 5.1 Tuesday, December 27, 2016

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Top new questions this week:
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[Partitioning a number into consecutive integers] http://mathematica.stackexchange.com/questions/134252/partitioning-a-number-into-consecutive-integers

Consider n=45; then

Question: how to ﬁnd all representations of a given positive integer n as a sum of ...

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[Why is my GIF shaky?] http://mathematica.stackexchange.com/questions/134272/why-is-my-gif-shaky

As you can see, the circles are shaking vertically as they approaching each other. Why is that?

The code:

g = Table[
Graphics[{Thickness[0.01],
Table[{ Circle[{0 + x, 0}, r],  ...

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[Can Mathematica edit large binary ﬁles in-place?] http://mathematica.stackexchange.com/questions/133973/can-mathematica-edit-large-binary-files-in-place

I have a very large binary data ﬁle (several hundred GB) which I would like to edit using Mathematica. The only edits required are a few isolated byte replacements—no insertions or deletions. Is it ...

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[Solving chess bishop problem] http://mathematica.stackexchange.com/questions/134218/solving-chess-bishop-problem

I have generalized the problem in this way where I have a list

list=Tuples[Range[8],2]

I want to ﬁnd the largest sublist in which the addition of the two entries for any two elements of the ...

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[How to get such rule with a elegant method] http://mathematica.stackexchange.com/questions/134227/how-to-get-such-rule-with-a-elegant-method

I have two lists:

list={{1,2,3,5},{5,3,9,11,12},{5,9,10,16}};
list2={{7,89},{96,5},{-6,-98}};

This is the expected result.

{{1-&gt;{7,89},2-&gt;{7,89},3-&gt;{7,89},5-&gt;{7,89}},
...

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[Pseudo-currying in one line] http://mathematica.stackexchange.com/questions/134315/pseudo-currying-in-one-line

Often when I’m writing OOP code using an object-manager association I ﬁnd myself doing something akin to currying the arguments to some form of delegate object or head. (Building a one-argument ...

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[How to create a multi-graphics plot (i.e. the decomposition of phase plane portrait) with well-organized structure?] http://mathematica.stackexchange.com/questions/134228/how-to-create-a-multi-graphics-plot-i-e-the-decomposition-of-phase-plane-portr

Background

I am trying to create a three-graphics plot using the command GraphicsGrid[] to show the decomposition of the phase plane portrait; unfortunately, the plot created is very ugly since the ...

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

[Finding Limits in several variables] http://mathematica.stackexchange.com/questions/21544/finding-limits-in-several-variables

Is there a way to ﬁnd a limit of a multivariable function, like

with Mathematica?

When $$f$$ is continuous, we can use

...

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

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

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

[Graph that shows how symbols are used in an expression] http://mathematica.stackexchange.com/questions/134180/graph-that-shows-how-symbols-are-used-in-an-expression

I would like to make a graph to show how symbols build up an expression. For example, the matrix multiplication


\left(
\begin{array}{ccc}
a &amp; b &amp; c \\
d &amp; e &amp; f \\
\end{array}
...

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I have a such custom function:

MyCopy := DynamicModule[{from, to},
Print@Grid[{{FileNameSetter[Dynamic[from], "Directory"],
Dynamic[from]}, {FileNameSetter[Dynamic[to], "Directory"],
...

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[General solution of inscribed square problem] http://mathematica.stackexchange.com/questions/134237/general-solution-of-inscribed-square-problem

There is my earlier question about Inscribed square problem

Now I tried to ﬁnd the general solution for any curve $$f(x,y)=0$$.

For instance :

$$\qquad \left (x^2+y^2-1\right )^3-x^2 y^3=0$$

...

### 5.2 Tuesday, December 20, 2016

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Top new questions this week:
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[How can I work with RawArray?] http://mathematica.stackexchange.com/questions/133666/how-can-i-work-with-rawarray

RawArray seems to be able to eﬃciently hold integer and ﬂoating point data of various sizes.

What is RawArray good for? How can we use it?

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[Random points around the given curve] http://mathematica.stackexchange.com/questions/133682/random-points-around-the-given-curve

How to plot a random points around the following Helix curve?

 ParametricPlot3D[{6 Cos[t], 6 Sin[t], t}, {t, -2 π, 4 π},
PlotTheme -&gt; "Detailed", PlotStyle -&gt; {Blue, Thickness[Large]},
...

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[Intuition behind FoldPair and SequenceFold?] http://mathematica.stackexchange.com/questions/133625/intuition-behind-foldpair-and-sequencefold

In trawling through the documentation I’ve found the functions FoldPairList and SequenceFoldList. Examples are given of how to use FoldPairList:

Partition a list into sublists of diﬀerent lengths ...

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[Product of two lists] http://mathematica.stackexchange.com/questions/133723/product-of-two-lists

L1 := {{a, b}, {c, d}, {e, f}}
L2 := {{g, h, i}, {j, k, q}}

I need the result

{{{a g, a h, a i}, {c g, c h, c i}, {e g, e h, e i}},
{{b j, b k, b q}, {d j, d k, d  ...


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[Is there something similar to seaborn stripplot in mathematica] http://mathematica.stackexchange.com/questions/133634/is-there-something-similar-to-seaborn-stripplot-in-mathematica

Is there something similar to seaborn stripplot in mathematica? The graph I am trying to make is like this:

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[Collapsible Tree] http://mathematica.stackexchange.com/questions/133492/collapsible-tree

Has somebody tried to program for data visualization an interactive Collapsible Tree like shown here: http://bl.ocks.org/mbostock/4339083. This implements the Reingold-Tilford algorithm.

...

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[FindDistributionParameters fails with custom distribution which cannot be evaluated symbolically] http://mathematica.stackexchange.com/questions/133456/finddistributionparameters-fails-with-custom-distribution-which-cannot-be-evalua

Context

I am interested in measuring the dark energy equation of state of the universe while ﬁtting the PDF of density in cells. This involves ﬁtting a one parameter PDF to some data.

Following ...

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

[How can I draw the Olympic rings with Mathematica?] http://mathematica.stackexchange.com/questions/8885/how-can-i-draw-the-olympic-rings-with-mathematica

How can I draw the 5 interlocking Olympic rings with Mathematica?

(SVG version)

Edit

Hard choice, but some pretty cool answers here. I didn’t have 3D answers in mind when I posted the question, ...

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

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

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

[Symbolic Weak Form] http://mathematica.stackexchange.com/questions/133575/symbolic-weak-form

Usually I write the weak form by hand for my FEM code, but it’s a little annoying and mechanic sometimes.

So, I wonder, is there any way to generate the symbolic weak form in Mathematica? For ...

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[Why is Minimize spinning?] http://mathematica.stackexchange.com/questions/133789/why-is-minimize-spinning

The command

Minimize[a^2 + b^2 + c^2 + a*b + b*c + a*c -
(a + b - c)*Sqrt[2 a*b + b*c + a*c] - (b + c - a)* Sqrt[2 b*c + b*a + a*c] -
(a + c - b)*Sqrt[2 a*c + a*b + b*c], a &gt;= 0 &amp;&amp; b  ...

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[How to export an MXNet?] http://mathematica.stackexchange.com/questions/133857/how-to-export-an-mxnet

I was hoping there was some way to generate the .params and .json ﬁle needed to deﬁne an MXNet model, from a network trained using NetTrain[] in Mathematica:

I see these functions in the ...

### 5.3 Tuesday, December 13, 2016

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Top new questions this week:
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Consider the following query:

Range[5] // Query[Select[EvenQ] /* Append[1], f]

(* {f[2], f[4], 1} *)

It selects the even numbers, applies f to them and ﬁnally appends 1 to the list. As expected, ...

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[Why does Mathematica think this series doesn’t converge?] http://mathematica.stackexchange.com/questions/132982/why-does-mathematica-think-this-series-doesnt-converge

Bug introduced in 10.0 and persisting through 11.0 (reported as CASE:3790525)

Here’s a simple series:

Sum[t^k DiscreteDelta[k]/k!,{k,0,Infinity}]

Mathematica says that it doesn’t converge. But ...

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[Joining two lists with relational operators] http://mathematica.stackexchange.com/questions/132928/joining-two-lists-with-relational-operators

I have two lists liste = {x, -y, y, -z} and
listv = {1, -2, 3, -4}, which represent the inequities
obtained evaluating liste - listv &lt;= 0. How do I reassemble or
join those two separate lists into  ...

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[What assumptions do I need to make Mathematica integrate a function?] http://mathematica.stackexchange.com/questions/133052/what-assumptions-do-i-need-to-make-mathematica-integrate-a-function

When I feed Mathematica the following integral:

Integrate[Sqrt[(A - x) (B - x)/x], {x, 0, B}]

it spits it back out without evaluating it. However, it can evaluate the integral

Integrate[Sqrt[(2 -  ...

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[Do Apple Watch + Mathematica integrations still work?] http://mathematica.stackexchange.com/questions/133358/do-apple-watch-mathematica-integrations-still-work

I tried to follow this blog post: Instant Apps for Apple Watch, but none of the examples given worked, instead, they would simply hang on the ”loading” screen.

Can anyone verify if this ...

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[Locate Start and End Positions of Repeated Sequences in a list] http://mathematica.stackexchange.com/questions/133164/locate-start-and-end-positions-of-repeated-sequences-in-a-list

ListA = 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 12, 12, 12, 14, 14, 14, 12, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, ...

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A common ”trick” in neural network training is to train an autoencoder using a ”degraded” sample as input and the original sample as target output. The layer type DropoutLayer[] is made for this ...

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

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

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

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

I am new to Mathematica, and using version 8.0.

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

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

[Mathematica script, called from Windows task scheduler, does not export graphics] http://mathematica.stackexchange.com/questions/133075/mathematica-script-called-from-windows-task-scheduler-does-not-export-graphics

When I run the following script from command line,

Needs["JLink"];
ConnectToFrontEnd[];
resultChart = UseFrontEnd[JuliaSetPlot[0.365 - 0.37 I]];
UseFrontEnd[Export["test.png", resultChart]];

...

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[Is it possible to do matrix algebra symbolically?] http://mathematica.stackexchange.com/questions/132955/is-it-possible-to-do-matrix-algebra-symbolically

I’m reading a book that has the following theorem:

I am trying to make Mathematica perform these calculations for me. Is it possible to do it without having to declare the matrices? For ...

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[Making graphic objects disappear interactively] http://mathematica.stackexchange.com/questions/133256/making-graphic-objects-disappear-interactively

I am trying to create a program where dots on a plane disappear when an object passes over them. I am using EventHandler to code the arrow keys for control of the object. I want each dot to ...

- asked by Savannah S (1 vote)

### 5.4 Tuesday, December 6, 2016

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Top new questions this week:
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[How to ﬁnd arXiv articles] http://mathematica.stackexchange.com/questions/132685/how-to-find-arxiv-articles

I found at Twitter that is possible to search for arXiv articles with Mathematica:

E.g. the following code:

arXiv = ServiceConnect["ArXiv"];

articles = arXiv["Search", {"Query" -&gt;  ...

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A crucial step in self-driving car is to detect lane lines. I’m wondering whether this can be achieved robustly using Mathematica’s rich image processing tools.

For example how can I take camera ...

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[Neural Network for polynomial ﬁt] http://mathematica.stackexchange.com/questions/132546/neural-network-for-polynomial-fit

I’m trying to build up a neural network with Mathematica 11.0, that should ﬁt data which behaves like a polynom of third order. I thought that an NN with one or two hidden layers can ﬁt any ...

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[How to make notebooks suitable for the Documentation Center?] http://mathematica.stackexchange.com/questions/132392/how-to-make-notebooks-suitable-for-the-documentation-center

Normally, documentation meant to be integrated into the Documentation Center is built from special source notebooks.

According to the Workbench documentation, it should also be possible to use ...

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[Largest palindrome from given string] http://mathematica.stackexchange.com/questions/132834/largest-palindrome-from-given-string

Someone recently posted a request on LinkedIn for an algorithm to ﬁnd the largest palindrome from a given string.

I came up with this, which I believe does the trick, but I am wondering if there ...

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[Why Function is not identical to & in autocompilation?] http://mathematica.stackexchange.com/questions/132656/why-function-is-not-identical-to-in-autocompilation

Here is the example, copied from here

square = Function[x, x^2];
square1 = #^2 &amp;;

the timing and unpacking status shows

data = RandomReal[0, 10, 10000];

...

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[Analytic solution to Newtonian gravity diﬀerential equation] http://mathematica.stackexchange.com/questions/132875/analytic-solution-to-newtonian-gravity-differential-equation

I was told that I could obtain an analytic solution to a particle falling under the inﬂuence of Newtonian gravity by using DSolveValue.

What I am given

$$G = M = m = 1$$ $$M$$ is a point mass at $$z=0$$ ...

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

[Unit Discovery: Is this some sort of a sick joke?] http://mathematica.stackexchange.com/questions/124745/unit-discovery-is-this-some-sort-of-a-sick-joke

Alright, let’s have some fun here. I am essentially following the documentation by Wolfram, just looking at diﬀerent quantities.

N[UnitConvert[Quantity["earth's gravity"]]]

9.80665m/(s)^2

Hmm, ...

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[How can Mathematica be used to create images like these?] http://mathematica.stackexchange.com/questions/118992/how-can-mathematica-be-used-to-create-images-like-these

Here are two examples of artistic image interpolation using just black lines:

TRIANGULATION: ANGULAR CELEBRITIES DRAWN WITH A PEN Interpolation for Triangulation-represented Digital Image

The ...

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

[How to ﬁnd a value to make function positive and real?] http://mathematica.stackexchange.com/questions/132883/how-to-find-a-value-to-make-function-positive-and-real

Let

x=(((-3 + r) r^2 + a^2 (1 + r)) Csc[θ])/(a (-1 + r))

y=Sqrt[(a^2 (a^2 (1 + r)^2 + 2 r^2 (-3 + r^2)) +
a^4 (-1 + r)^2 Cos[θ]^2 - ((-3 + r) r^2 +
a^2 (1 + r))^2 Csc[θ]^2)/(a^2 (-1 + r)^2)]

...

- asked by MrDi (1 vote)

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[Creating an automatic code feedback for class] http://mathematica.stackexchange.com/questions/132880/creating-an-automatic-code-feedback-for-class

I’m trying to create a server application that accepts uploaded Mathematica ﬁles (that follow a certain API), then run a few tests on modules deﬁned within those ﬁles. This is for a course where ...

- asked by michael99man (1 vote)

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[Nontrivial background removal] http://mathematica.stackexchange.com/questions/132844/nontrivial-background-removal

I have an image of a product on a poorly made green screen and need to segment out just the product:

The problem is that it contains a mirror, so simple color-based methods are not enough.

I tried ...

### 5.5 Tuesday, November 29, 2016

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Top new questions this week:
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[PacletInfo.m documentation project] http://mathematica.stackexchange.com/questions/132064/pacletinfo-m-documentation-project

Packages can be made into paclets, which provides easy distribution and versioning. The paclet metadata is in the PacletInfo.m ﬁle. The PacletInfo settings also determine how the paclet can extend ...

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[Replace custom functions, leave built in functions untouched?] http://mathematica.stackexchange.com/questions/131938/replace-custom-functions-leave-built-in-functions-untouched


I have three expressions a[x, y], b[x, y], c[x, y] that act as
placeholders for functions of two variables x,y. Consider the following substitution:

a[x, y]/(b[x, y] c[x, y]) /. f_[x1_, y1_] :&gt;  ...

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[Why CompilationTarget -¿ C is slower than directly writing with C?] http://mathematica.stackexchange.com/questions/132130/why-compilationtarget-c-is-slower-than-directly-writing-with-c

Probably a hard question, but I think it’s better to cry out loud.

I’ve hesitated for a while about whether I should post this in StackOverﬂow with a c tag or not, but ﬁnally decide to keep it ...

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[Detecting kernel initialization] http://mathematica.stackexchange.com/questions/132212/detecting-kernel-initialization

Certain operations do not work during kernel initialization. Code from Kernel/init.m, the Autoload directory, or packages set to autoload may evaluate at initialization time.

Is there a way to ...

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[How can I change the default ﬁle type for ”Save Selection As”] http://mathematica.stackexchange.com/questions/132224/how-can-i-change-the-default-file-type-for-save-selection-as

When using the menu item File - Save Selection As, the default ﬁle type is PDF. Is there any way to change the default to something else, for example PNG?

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[How to obtain the ViewPoint] http://mathematica.stackexchange.com/questions/132228/how-to-obtain-the-viewpoint

Normally, I used ViewPoint in the code in Plot3D. Most of the time, I will use mouse to rotate the 3D object to get a better view point. The problem is, when I ﬁnd the best view point for me, is ...

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[Wonky Solutions to Schrödinger Equation with Box Barrier] http://mathematica.stackexchange.com/questions/131854/wonky-solutions-to-schr%C3%B6dinger-equation-with-box-barrier

I’m trying to solve the Schrödinger equation using NDSolve in a case where there is a potential box barrier. The initial condition is a cosine wave, and for boundary conditions I require that the ...

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

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

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

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

I’m trying to expedite some quantum mechanical calculations by running them through Mathematica. Expectation values and stuﬀ like that. When I say, for example,

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

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

[Is it possible to change the text cursor’s shape and color?] http://mathematica.stackexchange.com/questions/132322/is-it-possible-to-change-the-text-cursors-shape-and-color

I ﬁnd it visually pleasant to reverse the background and foreground colors when working on a notebook; as shown below, in fact, it’s almost a requirement after working long hours on the same ...

- asked by Jerome Ibanes (1 vote)

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[FindClusters doesn’t accept custom DistanceFunction] http://mathematica.stackexchange.com/questions/132287/findclusters-doesnt-accept-custom-distancefunction

I have a problem with using custom DistanceFunction in FindClusters. To make the issue as simple as possible, consider clustering odd &amp; even numbers in the following way:

...

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[FrameLabel is Broken for ArrayPlot and MatrixPlot] http://mathematica.stackexchange.com/questions/132008/framelabel-is-broken-for-arrayplot-and-matrixplot

In version 11.0.1 the documentation for FrameLabel states its format is

left, right, bottom, top

However, it appears that this is not the case for MatrixPlot.

...

### 5.6 Tuesday, November 22, 2016

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

[Create the source image for this cool animated illusion] http://mathematica.stackexchange.com/questions/131644/create-the-source-image-for-this-cool-animated-illusion

Have a look at this very awesome video:

You have a vertically discretized image, which is composed of 5 or 6 images, which are shifted by an increment, as ...

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[Restarting Mathematica automatically] http://mathematica.stackexchange.com/questions/131573/restarting-mathematica-automatically

I run a large computation in a loop. At each cycle of the loop I produce large arrays that I save on a disk. At each cycle I would like to Quit Mathematica and then restart automatically, loading ...

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[How to handle package dependencies?] http://mathematica.stackexchange.com/questions/131567/how-to-handle-package-dependencies

When an application written in C++ depends on some libraries, the libraries are usually shipped together with the application. Two applications that depend on the same library will not share the same ...

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[How to sample many points below a curve?] http://mathematica.stackexchange.com/questions/131755/how-to-sample-many-points-below-a-curve

I have plotted the curve, and I wanted to take 1000 points in the shaded area uniformly. How can I make it?

Plot[1/π Cos[θ]^2, {θ, 0, 2 π}, Filling -&gt; Bottom]

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[how to style multi-value interpolation function plot?] http://mathematica.stackexchange.com/questions/131516/how-to-style-multi-value-interpolation-function-plot

Is there a cleaner way to apply diﬀerent styles to the diﬀerent channels of a multi value interpolation function?

here is a 2-output interpolation function:

f = Interpolation[Table[ {x, N@{Sin[x],  ...

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[Backtesting a Probability of Default (PD) model] http://mathematica.stackexchange.com/questions/131347/backtesting-a-probability-of-default-pd-model

Background

PD models

Financial institutions use Probability of Default (PD) models for various purposes such as client acceptance, provisioning and regulatory capital calculation as required by the ...

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[Display bug in Dataset’s UnitConvert handling] http://mathematica.stackexchange.com/questions/131332/display-bug-in-datasets-unitconvert-handling

Bug introduced in 11.0.1 (or possibly 11.0.0)

Is this yet another annoying regression in v11 Dataset type handling? The display form seems to be a formatting bug:

The numerator and denominator of ...

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

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

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

 ParametricPlot3D[{r Cos[Theta]], r Sin[\[Theta]], ... - asked by Matthew Leingang (85 votes), answered by Heike (74 votes) —————————- [How to create a new ”person curve”?] http://mathematica.stackexchange.com/questions/17704/how-to-create-a-new-person-curve Wolfram—Alpha has a whole collection¹ of parametric curves that create images of famous people. To see them, enter WolframAlpha[”person curve”] into a Mathematica notebook, or person curve into ... - asked by Simon (61 votes), answered by Vitaliy Kaurov (30 votes) ================================== Can you answer these? ================================== [Unix-like reference to parent and root Association?] http://mathematica.stackexchange.com/questions/131337/unix-like-reference-to-parent-and-root-association Is there a syntax or function to reference parent and root when querying nested Associations similar to Unix' ".." and "/", eg "cd ../../mydir". ? Here’s a typical application of the root ... - asked by alancalvitti (3 votes) —————————- [Strange behaviour of FullSimplify when checking an equality of SparseArray’s] http://mathematica.stackexchange.com/questions/131400/strange-behaviour-of-fullsimplify-when-checking-an-equality-of-sparsearrays I stumbled upon the following strange behaviour. Disclaimer: I present the simplest instance that I could ﬁnd in which some behaviour occurs that I ﬁrst noticed in a diﬀerent, more complicated ... - asked by Jules Lamers (1 vote) —————————- [ListPlot PlotRange Ignored with all Missing or empty data] http://mathematica.stackexchange.com/questions/131321/listplot-plotrange-ignored-with-all-missing-or-empty-data I have a function that uses ListPlot to draw a custom plot. When a data value is not applicable I pass in Missing to prevent ListPlot and its Prolog option from displaying the point the function will ... - asked by Edmund (3 votes) ### 5.7 Tuesday, November 15, 2016 ================================== Top new questions this week: ================================== [Why (and when) does pattern matching with f[__] perform MUCH more quickly than _f?] http://mathematica.stackexchange.com/questions/130984/why-and-when-does-pattern-matching-with-f-perform-much-more-quickly-than Consider this expression in Mathematica 10.3 (and above) on MacOS X: expr = a b c d e f g h i j k l m n o p q r s t myG[u] myF[a, b] Now compare the time it takes to apply the following ... - asked by QuantumDot (22 votes), answered by WReach (17 votes) —————————- [Getting wrong limit with Bessel] http://mathematica.stackexchange.com/questions/130741/getting-wrong-limit-with-bessel I computed a following limit (related to the asymptotic expansion of the sequence A000009 - number of partitions of n into distinct parts) Expand[Limit[(((π BesselI[1, (Sqrt[1/24 + n] ... - asked by Vaclav Kotesovec (11 votes), answered by Akku14 (9 votes) —————————- [Join lists by observing x-value] http://mathematica.stackexchange.com/questions/130903/join-lists-by-observing-x-value Hi everybody I have as a small test with two datasets (normally I have 100 datasets with 4100 brackets): Dataset1={{20,1},{30, 1.3}, {40, 0.4}, {50, 0.9}} Dataset2={{30, 1.2}, {40, 1}, {50, 0.4}, ... - asked by Jacccy (10 votes), answered by ubpdqn (13 votes) —————————- [How to distribute Mathematica packages as paclets?] http://mathematica.stackexchange.com/questions/131101/how-to-distribute-mathematica-packages-as-paclets Mathematica does have a nice package manager. Packages are called paclets, and they can be managed using the functions from the PacletManager‘ context. How can I package up my own packages as ... - asked by Szabolcs (9 votes), answered by Szabolcs (7 votes) —————————- [Does function call via @ ignore HoldFirst attribute?] http://mathematica.stackexchange.com/questions/130889/does-function-call-via-ignore-holdfirst-attribute I was trying to test whether using func[x,y] is the same as func[#,y]&amp;@x: SetAttributes[test, HoldFirst] test[1 + 2 - 3, 5 - 5] test[#, 5 - 5] &amp;@(1 + 2 - 3) test[1 + 2 - 3, 0] ... - asked by Ruslan (8 votes), answered by m_goldberg (9 votes) —————————- [Graph visualization: Leave gap between vertex and endpoint of edge] http://mathematica.stackexchange.com/questions/130821/graph-visualization-leave-gap-between-vertex-and-endpoint-of-edge This is a nice graph: g = CycleGraph[4]; Graph[g, VertexCoordinates -&gt; {{0, 0}, {0, 1}, {1, 1}, {1, 0}}, VertexLabels -&gt; Placed["Name", Center], VertexSize -&gt; Medium, EdgeShapeFunction ... - asked by cyrille.piatecki (8 votes), answered by kglr (12 votes) —————————- [Help ﬁnding the centre of a faint, incomplete circle?] http://mathematica.stackexchange.com/questions/130787/help-finding-the-centre-of-a-faint-incomplete-circle so I found a program in the answers to this question that I thought was brilliant, so here it is applied to my situation: I have the image and here’s the code: ... - asked by Mason (8 votes) ================================== Greatest hits from previous weeks: ================================== [How can Mathematica be used to create images like these?] http://mathematica.stackexchange.com/questions/118992/how-can-mathematica-be-used-to-create-images-like-these Here are two examples of artistic image interpolation using just black lines: TRIANGULATION: ANGULAR CELEBRITIES DRAWN WITH A PEN Interpolation for Triangulation-represented Digital Image The ... - asked by R Hall (28 votes), answered by MarcoB (29 votes) —————————- [How do you make a Neural Net?] http://mathematica.stackexchange.com/questions/123458/how-do-you-make-a-neural-net In the new Mathematica release (v11), NeuralNetworks is one of the new main features. However, the documentation isn’t that clear on what function should be used in a Net. The documentation on ... - asked by JHM (22 votes), answered by Searke (24 votes) ================================== Can you answer these? ================================== [Understanding the structure of an InterpolatingFunction] http://mathematica.stackexchange.com/questions/131063/understanding-the-structure-of-an-interpolatingfunction FunctionInterpolation[x^2, {x, 0, 9}] // InputForm returns: InterpolatingFunction[ 0., 9., 5, 3, 0, 13, 4, 0, 0, 0, 0, Automatic, , , False, 0., 0.75, 1.5, 2.25, 3., 3.75, ... - asked by anderstood (1 vote) —————————- [Is it possible to create .stp 3D model from Graphics3D?] http://mathematica.stackexchange.com/questions/130883/is-it-possible-to-create-stp-3d-model-from-graphics3d I want to create some 3D solid model by Mathematica, and then export it into stp (step) format for further ﬁnite element or ﬁnite volume analysis in Fluent/ANSYS or Abaqus. But so far to me, it ... - asked by user6043040 (3 votes) —————————- [Time constrained loop unit] http://mathematica.stackexchange.com/questions/131159/time-constrained-loop-unit I have a particularly diﬃcult loop, in that it consists of two variables looping and sowing the result if a criteria is met. Overall it works for me, but some certain values for my variables take ... - asked by Castle (2 votes) ### 5.8 Tuesday, November 8, 2016 ================================== Top new questions this week: ================================== [For a better animation of the solution from NDSolve] http://mathematica.stackexchange.com/questions/130502/for-a-better-animation-of-the-solution-from-ndsolve I obtained a numerical solution from the following code with NDSolve L = 20; tmax = 27; \[Sigma] = 2; myfun = First[h /. NDSolve[{D[h[x, y, t], t] + Div[h[x, y, t]^3*Grad[Laplacian[h[x, y, t], {x, ... - asked by jsxs (12 votes), answered by Nasser (14 votes) —————————- [A puzzling result of ”FullSimplify”] http://mathematica.stackexchange.com/questions/130606/a-puzzling-result-of-fullsimplify When I input: FullSimplify[(1 - a^2)/b^2, a^2 + b^2 == 1] the result is the ideal answer 1； However，if I input: FullSimplify[(1 - b^2)/a^2, a^2 + b^2 == 1] the result is (1 - b^2)/a^2， ... - asked by dabuyang (11 votes), answered by Bob Hanlon (7 votes) —————————- [ImageFeatureTrack or ImageDisplacements to measure average object velocities in images] http://mathematica.stackexchange.com/questions/130391/imagefeaturetrack-or-imagedisplacements-to-measure-average-object-velocities-in I have as example a set of 30 gray scale images (8bit, 568*478 pixels, they are avalable here: http://tinyurl.com/zckyv9w where bright objects on dark background move from image to image mainly ... - asked by mrz (9 votes), answered by Simon Woods (10 votes) —————————- [Documentation Tools: Don’t put web URL in user package docs] http://mathematica.stackexchange.com/questions/130515/documentation-tools-dont-put-web-url-in-user-package-docs I am exploring the Workbench documentation tools for the ﬁrst time and one of the diﬃculties I encountered was that every generated (compiled) documentation page includes weblinks. These point to ... - asked by Szabolcs (9 votes) —————————- [How to make plots ’blacker’?] http://mathematica.stackexchange.com/questions/130471/how-to-make-plots-blacker I need to make a contour plot for publication, but even if I set ContourStyle-&gt;Black, the 'black' plots and the axes are very faint. When I export the figure in svg and open it in some ... - asked by Physicist (9 votes), answered by Michael E2 (10 votes) —————————- [How to specify algebraic relations between objects?] http://mathematica.stackexchange.com/questions/130258/how-to-specify-algebraic-relations-between-objects so I’m wanting to screw around a bit with Geometric Algebra in Mathematica. To start, I want to create some basis objects: $$e_1,~ e_2,~e_3$$ and then specify the relations between them which are - asked by Mason (9 votes), answered by march (9 votes) —————————- [Crack it If you Can? BUT in the BEST way] http://mathematica.stackexchange.com/questions/130566/crack-it-if-you-can-but-in-the-best-way From the Wolfram Community: Hello everyone, A little while ago I was asked to solve this ”safe cracker” puzzle, a sweet example of a coﬀee table puzzle. The basic gist of this puzzle is that it ... - asked by Youphyso (8 votes), answered by george2079 (4 votes) ================================== Greatest hits from previous weeks: ================================== [Writing a word with straight lines] http://mathematica.stackexchange.com/questions/113403/writing-a-word-with-straight-lines Here is an interesting way to write a word: (it is from a poster for the International Museum Day 2006; I believe it even won an award at an international design competition) by Boris Ljubicic. ... - asked by VividD (72 votes), answered by Anton Antonov (34 votes) —————————- [Where can I ﬁnd examples of good Mathematica programming practice?] http://mathematica.stackexchange.com/questions/18/where-can-i-find-examples-of-good-mathematica-programming-practice I consider myself a pretty good Mathematica programmer, but I’m always looking out for ways to either improve my way of doing things in Mathematica, or to see if there’s something nifty that I haven’t ... - asked by J. M. (441 votes), answered by faysou (396 votes) ================================== Can you answer these? ================================== [Passing boolean parameters to a .NET Method using NETLink] http://mathematica.stackexchange.com/questions/130658/passing-boolean-parameters-to-a-net-method-using-netlink According to the NETLink documentation, NETLink automatically handles type conversions from Mathematica to a .NET dll. One of the issues I have is that the .NET method I want to use expects a Boolean ... - asked by user39464 (1 vote) —————————- [ParametricPlot3D Self Intersection] http://mathematica.stackexchange.com/questions/130460/parametricplot3d-self-intersection I would like to know where my ParametricPlot3D intersects itself and to extract all intersections (points, lines, surfaces...) to animate them by changing P: ParametricPlot3D[{fX[u,v,P], fY[u,v,P], ... - asked by chkone (3 votes) —————————- [Faster solution to combinatorial problem of two-part contractions] http://mathematica.stackexchange.com/questions/130598/faster-solution-to-combinatorial-problem-of-two-part-contractions Given a list of elements I need all possible pairings of elements with a leading factor that describes the number of permutations. A (ugly but) working version would be: list = {a, b, c, d}; res = ... - asked by pbx (2 votes) ### 5.9 Tuesday, November 1, 2016 ================================== Top new questions this week: ================================== [Huge bug involving MultinormalDistribution?] http://mathematica.stackexchange.com/questions/129916/huge-bug-involving-multinormaldistribution Bug introduced in 8.0 or earlier and persisting through 11.0.1 I found a strange behavior regarding the CDF of the bivariate Normal distribution ... - asked by fwgb (21 votes), answered by Eric Towers (19 votes) —————————- [GeoDistance - higher spatial resolution / precision?] http://mathematica.stackexchange.com/questions/130044/geodistance-higher-spatial-resolution-precision I’m having a small problem with GeoDistance. I’ve chosen a target city – San Francisco – and I’ve computed distances from SF to ﬁve other cities. Then I draw circles around each city, with radius ... - asked by ConvexMartian (9 votes), answered by jose (4 votes) —————————- [How to extract the ﬁrst dimension in TimeSeries?] http://mathematica.stackexchange.com/questions/129836/how-to-extract-the-first-dimension-in-timeseries I want to extract the ﬁrst dimension in TimeSeries，for example: So I use this code: data = Normal@AudioLocalMeasurements[ExampleData[{"Audio", "PianoScale"}],"MFCC"]; Thread[{data[[All, 1]], ... - asked by partida (9 votes), answered by kglr (6 votes) —————————- [How to recover Pauli matrices properties in Mathematica?] http://mathematica.stackexchange.com/questions/129799/how-to-recover-pauli-matrices-properties-in-mathematica I want to do a cross or dot product involving a vector of Pauli matrices σ=(σ1,σ2,σ3); for example, σxσ=2iσ or σ.σ=3I. Is there a simple way to do these operations? - asked by user3654016 (8 votes), answered by corey979 (10 votes) —————————- [Flatten sublists within a bigger list] http://mathematica.stackexchange.com/questions/130011/flatten-sublists-within-a-bigger-list Really sorry if this question is a duplicate. I couldn’t ﬁnd exactly what I was looking for. Here is a list I have: {{{0. + 0.1875 I, 0. + 0.105469 I, 0. + 0.03125 I, 0. + 0.00390625 I, 0. + ... - asked by jrekier (7 votes), answered by Edmund (6 votes) —————————- [7-dimensional cross product] http://mathematica.stackexchange.com/questions/129863/7-dimensional-cross-product How to deﬁne a 7-dimensional cross product? \begin{aligned}\mathbf {x} \times \mathbf {y} =(x_{2}y_{4}-x_{4}y_{2}+x_{3}y_{7}-x_{7}y_{3}+x_{5}y_{6}-x_{6}y_{5})\,&amp;\mathbf {e} ... - asked by corey979 (7 votes), answered by Sumit (4 votes) —————————- [How to draw a clock-diagram?] http://mathematica.stackexchange.com/questions/129960/how-to-draw-a-clock-diagram I found a clock-diagram in a paper, so I would like to draw it in Mathematica. The main trouble for me is the corresponding line segments on the circle. I would let the data1 lie the outside on the ... - asked by user123 (7 votes), answered by Feyre (7 votes) ================================== Greatest hits from previous weeks: ================================== [How can Mathematica be used to create images like these?] http://mathematica.stackexchange.com/questions/118992/how-can-mathematica-be-used-to-create-images-like-these Here are two examples of artistic image interpolation using just black lines: TRIANGULATION: ANGULAR CELEBRITIES DRAWN WITH A PEN Interpolation for Triangulation-represented Digital Image The ... - asked by R Hall (28 votes), answered by MarcoB (29 votes) —————————- [How to tell Mathematica that certain variables are real/imaginary, integer-valued, etc] http://mathematica.stackexchange.com/questions/66273/how-to-tell-mathematica-that-certain-variables-are-real-imaginary-integer-value I’m trying to expedite some quantum mechanical calculations by running them through Mathematica. Expectation values and stuﬀ like that. When I say, for example, u[x_] := Sqrt[2/L] * Sin[Pi * n * x / ... - asked by Matthew Brunetti (8 votes), answered by SquareOne (6 votes) ================================== Can you answer these? ================================== [How to Inset a legend in GeoGraphics with Scaled LegendMarkerSize?] http://mathematica.stackexchange.com/questions/130060/how-to-inset-a-legend-in-geographics-with-scaled-legendmarkersize I have a GeoGraphics where I am using Scaled in PointSize to include size information. I want to Inset a PointLegend that describes the sizes of the points. Outside of GeoGraphics I can do this by ... - asked by Edmund (2 votes) —————————- [NumberLinePlot with Exponential] http://mathematica.stackexchange.com/questions/129938/numberlineplot-with-exponential I have: Clear[f, x] f[x_] = Exp[1/x] Now, the question is "where is the derivative negative?" I managed to get the Reduce command to work by adding Reals. Reduce[f'[x] &lt; 0, x, Reals] Which ... - asked by David (3 votes) —————————- [Detect numbers on the image] http://mathematica.stackexchange.com/questions/129821/detect-numbers-on-the-image How to detect numbers on the following image I tried:  img=Import["http://imgur.com/TDbn7sB.png"] set = ImagePartition[img, Scaled[{1/20, 1/5}]] // Flatten then I tried Classify[] but it ... - asked by vito (3 votes) ### 5.10 Tuesday, October 25, 2016 ================================== Top new questions this week: ================================== [How to improve this plot?] http://mathematica.stackexchange.com/questions/129426/how-to-improve-this-plot In general, the quality of Mathematica graphics is beyond praise. However, the output of Plot3D command is somewhat unexpected in the following code. Let’s solve the Dirichlet problem for the ... - asked by user64494 (11 votes), answered by Simon Woods (16 votes) —————————- [Neural Networks: Does Mathematica (v11) experimental code support state-of-art Models?] http://mathematica.stackexchange.com/questions/129469/neural-networks-does-mathematica-v11-experimental-code-support-state-of-art-m Mathematica made a big step implementing Neural Networks. I checked some examples for deep learning (ChainNet), also the related link. I see that model structures such as LaNet can be developed. ... - asked by s.s.o (10 votes), answered by Alexey Golyshev (8 votes) —————————- [Converting Game of Life images to lists] http://mathematica.stackexchange.com/questions/129135/converting-game-of-life-images-to-lists I want to convert images of GoL conﬁgurations into binary matrices to run in Mathematica’s CellularAutomaton. I know that there’s a collection of GoL patterns in http://conwaylife.com and other ... - asked by andandandand (10 votes), answered by C. E. (5 votes) —————————- [JDBC-to-ODBC bridge gone. How to connect to SQL Server now in case of Windows Authentication?] http://mathematica.stackexchange.com/questions/129160/jdbc-to-odbc-bridge-gone-how-to-connect-to-sql-server-now-in-case-of-windows-au Connecting to our corporate SQL servers using JDBC never worked for me, perhaps related to the Windows Authentication method that is necessary in our network. However, I found out that conﬁguring the ... - asked by Sjoerd C. de Vries (8 votes), answered by Sjoerd C. de Vries (6 votes) —————————- [How to speed up calculations on big symbolic matrices?] http://mathematica.stackexchange.com/questions/129465/how-to-speed-up-calculations-on-big-symbolic-matrices this is my ﬁrst time posting something on a community of the StackExchange platform, so please feel free to correct me if I’m doing something wrong. :) Additionally you should probably know that I’m ... - asked by TSwift (8 votes) —————————- [How do I ’Join’ two Structured Datasets?] http://mathematica.stackexchange.com/questions/129116/how-do-i-join-two-structured-datasets Consider the following Datasets dsCompetitions with ﬁelds ”id”,”name”,”eventTypeId” dsEventTypes with ﬁelds ”id”, ”name” I want to join the datasets as follows using SQL pseudocode: SELECT ... - asked by nilo de roock (8 votes), answered by rcollyer (7 votes) —————————- [Why isn’t Orderless an Attribute of And?] http://mathematica.stackexchange.com/questions/129415/why-isnt-orderless-an-attribute-of-and In standard logic And is a commutative operator. Still, in Mathematica, And doesn’t have the Orderless attribute: Attributes[And] (* {Flat,HoldAll,OneIdentity,Protected} *) This may have not been ... - asked by Soldalma (7 votes), answered by JHM (6 votes) ================================== Greatest hits from previous weeks: ================================== [Programming the ﬁver game] http://mathematica.stackexchange.com/questions/120959/programming-the-fiver-game Obviously, even if I ask a lot of question I am, obviously, still a dummy!!!! I want to program the ﬁver game. It’s a very simple game played solitary on a $$5 \times 5$$ the rule is elementary : if ... - asked by cyrille.piatecki (12 votes), answered by Mr.Wizard (19 votes) —————————- [How to make an inkblot?] http://mathematica.stackexchange.com/questions/3345/how-to-make-an-inkblot How to eﬀectively create a polygon that looks like a realistic inkblot? So far, I could come up with this (borrowing from Ed Pegg Jr.’s Rorschach demonstration): RandomBlot[num_, opts___] := ... - asked by István Zachar (83 votes), answered by Sjoerd C. de Vries (46 votes) ================================== Can you answer these? ================================== [Counting the occurences of entries in a dataset columnwise] http://mathematica.stackexchange.com/questions/129459/counting-the-occurences-of-entries-in-a-dataset-columnwise Consider a dataset with some rows and considerably less columns (eg something like 10x3). Assume that the contents of the dataset cells are integers from some conveniently chosen range (eg 1 through ... - asked by user42582 (1 vote) —————————- [List, Association, and Dataset, according to what principles to choose which one to use?] http://mathematica.stackexchange.com/questions/129081/list-association-and-dataset-according-to-what-principles-to-choose-which-one List, Association and Dataset are three ’objects’ that can be used to store data in MMA. So when or under what conditions for one to decide to use each of them? - asked by Alexander Zeng (2 votes) —————————- [How to ArrayFlatten some matrix which have repeated element] http://mathematica.stackexchange.com/questions/129153/how-to-arrayflatten-some-matrix-which-have-repeated-element I have many such matrices(whose dimension are all 3*3.) like: list1={{0,3,0},{4,1,2},{0,5,0}}; list2={{0,6,0},{1,2,8},{0,7,0}}; list3={{0,1,0},{9,5,7},{0,11,0}}; list4={{0,2,0},{5,7,10},{0,12,0}}; ... - asked by yode (3 votes) ### 5.11 Tuesday, October 18, 2016 ================================== Top new questions this week: ================================== [Why removing a function and deﬁning it on the same line does not work?] http://mathematica.stackexchange.com/questions/128818/why-removing-a-function-and-defining-it-on-the-same-line-does-not-work Why do the two pieces of code below yield rather diﬀerent results? The only diﬀerence is that in the ﬁrst one the function deﬁnition is in the same line as the Remove command while in the second ... - asked by Fernando Saldanha (17 votes), answered by dan7geo (16 votes) —————————- [House of Santa Claus] http://mathematica.stackexchange.com/questions/128741/house-of-santa-claus The house of Santa Claus is an old German drawing game for small children. You have to draw a house in one line. You must not lift your pencil while drawing.  \color{red}{\text{You must not repeat a ... - asked by mrz (15 votes), answered by Dr. Wolfgang Hintze (9 votes) —————————- [how to get cell boundaries in the image] http://mathematica.stackexchange.com/questions/128596/how-to-get-cell-boundaries-in-the-image I have a microscope image of some animal tissue and wish to get the contours for all the cells that are present in the image. the cells are connected to the neighbouring cells via these contours. At ... - asked by Ali Hashmi (10 votes), answered by corey979 (13 votes) —————————- [Numerically solve the initial value problem for the 1-D wave equation] http://mathematica.stackexchange.com/questions/128516/numerically-solve-the-initial-value-problem-for-the-1-d-wave-equation I want to solve the standard 1-dimensional wave equation $$y_{xx}=y_{tt}$$ using NDSolve (for $$y(x,t)$$) with the following conditions: cond1 = Piecewise[{{1 - Abs[x - 1], Abs[x - 1] &lt; 1}, {0, Abs[x ... - asked by arcbloom (8 votes), answered by xzczd (7 votes) —————————- [Dataset Processing: eﬃcient ways to clean and merge sets for Life Sciences] http://mathematica.stackexchange.com/questions/128519/dataset-processing-efficient-ways-to-clean-and-merge-sets-for-life-sciences Dataset Processing (for Life Sciences) Note: a related, but distinct task is posted here ID Swapping: Eﬃcient use of a reference table to convert ID values. A common task, at least for me, ... - asked by SumNeuron (8 votes), answered by SumNeuron (5 votes) —————————- [Rotations of a number] http://mathematica.stackexchange.com/questions/128666/rotations-of-a-number If we start with a number like 1234 and produce the following sum 1234 + 123 + 12 + 1 = 1370. If we are given the 1370 can I retrieve the 1234? A similar question was migrated over to the Math.SE ... - asked by bobbym (8 votes), answered by J. M. (6 votes) —————————- [What’s wrong with the Sum function?] http://mathematica.stackexchange.com/questions/128534/whats-wrong-with-the-sum-function Here are the codes: f[n_]:=Sum[1,{K,0,n},{M,0,n-K},{La,0,K},{Lb,0,n-K-M},{Lc,0,M}]//Simplify g[n_]:=Sum[1,{La,0,n},{Lb,0,n-La},{Lc,0,n-La-Lb},{K,La,n-Lb},{M,Lc,n-K-Lb}]//Simplify f[x]/.x-&gt;5 ... - asked by lamberto (7 votes), answered by Bob Hanlon (3 votes) ================================== Greatest hits from previous weeks: ================================== [Creating legends for plots with multiple lines?] http://mathematica.stackexchange.com/questions/4025/creating-legends-for-plots-with-multiple-lines So I have a graph with multiple lists, for e.g. data = {{1,2}, {3,4}, {3,5}, {2,3} . . .} If I then do ListLinePlot[Table[{#1,Log[b,#2]}&amp;@@@data, {b,1,10,2}]] I have no way to generate a legend ... - asked by Eiyrioü von Kauyf (59 votes), answered by Jens (88 votes) —————————- [Exporting graphics to PDF - huge ﬁle] http://mathematica.stackexchange.com/questions/1542/exporting-graphics-to-pdf-huge-file I want to draw some basic surfaces, export them to PDF and include them in a LaTeX ﬁle. I create a simple 3D graphics object, for instance with  ParametricPlot3D[{r Cos[\[Theta]], r Sin[\[Theta]], ... - asked by Matthew Leingang (85 votes), answered by Heike (74 votes) ================================== Can you answer these? ================================== [Parallelizing code, any tips?] http://mathematica.stackexchange.com/questions/128905/parallelizing-code-any-tips I have access to a Linux cluster and I’m trying to use Parallelize to run the above bellow faster, but whenever I try to place Parallelize in any other parts, besides the loop, where I think it may ... - asked by Sergio Parreiras (2 votes) —————————- [Does Reduce have problems with greek symbols that lead to wrong results?] http://mathematica.stackexchange.com/questions/128965/does-reduce-have-problems-with-greek-symbols-that-lead-to-wrong-results I call Reduce on the following simple system of inequalities e = ((-4 + Sqrt[(-2 + λ)^2] + 3 λ) Log[p] + 4 λ Log[β])/(2 λ); Reduce[e &gt; 0 &amp;&amp; 1 &gt; λ &gt; 0 &amp;&amp; 1 &gt; p &gt; 0 ... - asked by klm (3 votes) —————————- [Full screen image in slideshow?] http://mathematica.stackexchange.com/questions/128875/full-screen-image-in-slideshow Is it possible to make an image ﬁll up and entire slide in a slideshow notebook so that there are no cell brackets or any white space around it at all (when viewed in presentation mode of course)? - asked by M.R. (1 vote) ### 5.12 Tuesday, October 11, 2016 ================================== Top new questions this week: ================================== [How to programmatically play an Audio object?] http://mathematica.stackexchange.com/questions/128147/how-to-programmatically-play-an-audio-object A Sound object can be programmatically played using EmitSound. Example: snd = ExampleData[{"Sound", "AltoFlute"}]; Button["Play!", EmitSound[snd]] What about an Audio object? - asked by Szabolcs (14 votes), answered by Szabolcs (9 votes) —————————- [TreePlot does not give a ”binary-looking” tree for a binary tree] http://mathematica.stackexchange.com/questions/128323/treeplot-does-not-give-a-binary-looking-tree-for-a-binary-tree I use the following code to generate a binary tree with root 1. TreePlot[{1 -&gt; 2, 1 -&gt; 3, 2 -&gt; 4, 2 -&gt; 5, 3 -&gt; 6, 3 -&gt; 7, 4 -&gt; 8, 4 -&gt; 9, 5 -&gt; 10, 5 -&gt; 11, 6 -&gt; ... - asked by Tony (13 votes), answered by WReach (19 votes) —————————- [Partition array without unpacking] http://mathematica.stackexchange.com/questions/128133/partition-array-without-unpacking What is the simplest way to partition a list into equal-length sublists, allow the last sublist to be shorter of necessary, and avoid unpacking? Partition doesn’t usually unpack: arr = RandomReal[1, ... - asked by Szabolcs (13 votes), answered by Szabolcs (7 votes) —————————- [Creating a simple Dock Cell that Fades In when Cursor Hover Over It] http://mathematica.stackexchange.com/questions/128025/creating-a-simple-dock-cell-that-fades-in-when-cursor-hover-over-it I like to create dock cells, that enhance the look of my notebooks. Do you know of a simple way to get the functionality in iBooks shown below in the video. I want the dock cell in Mathematica to ... - asked by Michael McCain (13 votes), answered by Karsten 7. (14 votes) —————————- [Why are Exp[3] and 2 treated diﬀerently within Complex?] http://mathematica.stackexchange.com/questions/128211/why-are-exp3-and-2-treated-differently-within-complex Why doesn’t the last command below split the complex number into its real and imaginary parts? Complex[2,2] (* 2 + 2 I *) Complex[N[Exp[3]], N[Exp[3]]] (* 20.0855 + 20.0855 I *) ... - asked by Fernando Saldanha (12 votes), answered by Szabolcs (18 votes) —————————- [KeyDrop does not respect Key in V11] http://mathematica.stackexchange.com/questions/128171/keydrop-does-not-respect-key-in-v11 KeyDrop[&lt;|a -&gt; 1|&gt;, Key[a]] &lt;|a -&gt; 1|&gt; KeyTake[&lt;|a -&gt; 1|&gt;, Key[a]] &lt;||&gt;  closely related but not the same: Unexpected behavior of KeyTake Are there any ... - asked by Kuba (11 votes), answered by Xavier (5 votes) —————————- [Strategies for creating 3D text] http://mathematica.stackexchange.com/questions/128412/strategies-for-creating-3d-text I am interested in using Mathematica to create 3D text for printing. I stumbled upon this answer which works very well in a slightly modiﬁed form: text3D[text_String, mult_] := ListPlot3D[ ... - asked by bobthechemist (10 votes), answered by J. M. (14 votes) ================================== Greatest hits from previous weeks: ================================== [Is it possible to export the equations from Mathematica to MATLAB?] http://mathematica.stackexchange.com/questions/14035/is-it-possible-to-export-the-equations-from-mathematica-to-matlab Is it possible to export the output expressions from Mathematica computations (e.g., equations) in valid MATLAB syntax? - asked by Seyhmus Güngören (24 votes), answered by R. M. (32 votes) —————————- [Labeling individual curves in Mathematica] http://mathematica.stackexchange.com/questions/4444/labeling-individual-curves-in-mathematica I need to create a plot for export and inclusion in a report. Is there a better way to label curves than PlotLegends? From what I’ve read and my personal experience, PlotLegends is pretty bad. Is ... - asked by Tianxiang Xiong (47 votes), answered by Artes (37 votes) ================================== Can you answer these? ================================== [Help: Reclassify] http://mathematica.stackexchange.com/questions/128194/help-reclassify Is it possible to improve the current ClassiﬁerFunction with more training data without running the previous training again? In this way i will be able to deal with very large datasets in chunks. - asked by user13892 (5 votes) —————————- [Pattern matching problem in version 11.01] http://mathematica.stackexchange.com/questions/128247/pattern-matching-problem-in-version-11-01 Consider this simple example: p1 = ListPlot3D[ Table[Sin[j^2 + i], {i, 0, Pi, Pi/5}, {j, 0, Pi, Pi/5}], Mesh -&gt; None, Axes -&gt; False, Boxed -&gt; False, ColorFunction -&gt; Hue]; p2 = ... - asked by xslittlegrass (8 votes) —————————- [CUDADot runs slowly and writes ”CUDALink experienced a kernel launch failure” with matrix size ¿ 3300] http://mathematica.stackexchange.com/questions/128124/cudadot-runs-slowly-and-writes-cudalink-experienced-a-kernel-launch-failure-wi I am trying to learn CUDA and start from the help examples. It turnes out that CPU calculation is much faster for matrix sizes &lt; 3200 than CUDA, while CUDADot gives the error for sizes > 3300. I ... - asked by luu (4 votes) ### 5.13 Tuesday, October 4, 2016 ================================== Top new questions this week: ================================== [UI performance with large image data] http://mathematica.stackexchange.com/questions/127523/ui-performance-with-large-image-data Some days ago, I built a small program for some of my colleagues to analyse cell images. One minor part of the user interface was the selection of the region of interest. The images are large and need ... - asked by halirutan (25 votes), answered by Kuba (21 votes) —————————- [Transform sphere to an ellipse in $$R^2$$] http://mathematica.stackexchange.com/questions/127645/transform-sphere-to-an-ellipse-in-r2 In Lay’s Linear Algebra and Its Applications textbook, he deﬁnes the matrix and claims that the transformation $$T(x)=A x$$ ... - asked by David (15 votes), answered by yarchik (17 votes) —————————- [Did Fibonacci slow down?] http://mathematica.stackexchange.com/questions/127876/did-fibonacci-slow-down For Fibonacci numbers we have a nice formula: We can implement that in Mathematica: a[n_]:= ... - asked by Fred Simons (13 votes), answered by Szabolcs (20 votes) —————————- [I would like to create a fractal by copying, scaling and rotating the initial element] http://mathematica.stackexchange.com/questions/127458/i-would-like-to-create-a-fractal-by-copying-scaling-and-rotating-the-initial-el I want to create a fractal, which looks like this: This is rule 150R, which can be found in NKS, page 439. However, instead of using a cellular automaton, I want to create this fractal from a ... - asked by Yuriy S (13 votes), answered by wxﬄes (13 votes) —————————- [Mathematica + Pythonika on the Raspberry pi] http://mathematica.stackexchange.com/questions/127802/mathematica-pythonika-on-the-raspberry-pi Due to the high availability of python code for the rpi, I’m trying to call python functions from Mathematica. I know that pythonika works well on OS X, but I can’t compile it on the Raspberry pi. ... - asked by elbOlita (12 votes), answered by elbOlita (13 votes) —————————- [How to map and sum a list fast?] http://mathematica.stackexchange.com/questions/127658/how-to-map-and-sum-a-list-fast The following takes a lot of memory and is slow: Timing[Total[Map[#^2 &amp;, Range[1, 100000000]]]] I suspect this is because it ﬁrst calculates and stores the whole list of squared numbers and ... - asked by Yrogirg (12 votes), answered by BlacKow (19 votes) —————————- [Implementing the Biham–Middleton–Levine traﬃc model as CellularAutomaton] http://mathematica.stackexchange.com/questions/127821/implementing-the-biham-middleton-levine-traffic-model-as-cellularautomaton In an attempt to understand how to make rules for CellularAutomaton[], I set out to try to implement the Biham–Middleton–Levine traﬃc model. It is a 2D, k=3 model with a 3x3 neighborhood, so the ... - asked by HJensen (10 votes), answered by C. E. (5 votes) ================================== Greatest hits from previous weeks: ================================== [What are the most common pitfalls awaiting new users?] http://mathematica.stackexchange.com/questions/18393/what-are-the-most-common-pitfalls-awaiting-new-users As you may already know, Mathematica is a wonderful piece of software. However, it has a few characteristics that tend to confuse new (and sometimes not-so-new) users. That can be clearly seen from ... - asked by Dr. belisarius (341 votes), answered by Michael E2 (197 votes) —————————- [How to make this beautiful animation] http://mathematica.stackexchange.com/questions/112700/how-to-make-this-beautiful-animation How to make an animation of following gif in Mathematica? Edit: The animation shown above was created by Charlie Deck in processing. And how to make 3D analog? I tried ﬁrst few steps line = ... - asked by vito (47 votes), answered by C. E. (50 votes) ================================== Can you answer these? ================================== [VectorPlot3D broken in Mathematica 11.0.1?] http://mathematica.stackexchange.com/questions/127724/vectorplot3d-broken-in-mathematica-11-0-1 Here is what I get when simply evaluating the example in the documentation: This is on Win7 x64. I can see some vectors if I do something like VectorPlot3D[{1, 1, 1}, {x, -1, 1}, {y, -1, 1}, {z, ... - asked by Pirx (5 votes) —————————- [Least squares approximation] http://mathematica.stackexchange.com/questions/127806/least-squares-approximation I have data points which is mydata = 0, 0, 1, 1, 2, 0; From this data, I need to do the least squares approximation by using Bernstein polynomials to produce a set of Bezier points. Before ... - asked by NKamaru (2 votes) —————————- [Matching key-value pair without converting to List in KeyValueMap] http://mathematica.stackexchange.com/questions/127860/matching-key-value-pair-without-converting-to-list-in-keyvaluemap I frequently use this method with KeyValueMap in order to match and refer to named parts (ie, ”myKey”, ”myValue”) EDIT: to refer to named parts in the function f without an external function ... - asked by alancalvitti (1 vote) ### 5.14 Tuesday, September 27, 2016 ================================== Top new questions this week: ================================== [Should I always be using Module in functions unless I explicitly want global variables?] http://mathematica.stackexchange.com/questions/126877/should-i-always-be-using-module-in-functions-unless-i-explicitly-want-global-var I deﬁne functions a ton. In the past, I’ve mostly just deﬁned my functions like: myFunc[var1_]:=( var2=var1^2; Return@var2; ) And I haven’t run into too much trouble. If I wanted to be really ... - asked by YungHummmma (15 votes), answered by WReach (18 votes) —————————- [Why this real integral yields imaginary results?] http://mathematica.stackexchange.com/questions/127301/why-this-real-integral-yields-imaginary-results Integrate[(y - y^2 + x - x^2 + 2*x*y)/(1 - x - y),{x,0,1},{y, 0, 1}] The above integral yields -1-4Iπ/3 in Mathematica. Since the integrand is real (although divergent at some points), how does ... - asked by Chong Wang (12 votes), answered by bbgodfrey (12 votes) —————————- [Would it be a good idea to use Failure and FailureQ in own code] http://mathematica.stackexchange.com/questions/126908/would-it-be-a-good-idea-to-use-failure-and-failureq-in-own-code Since version 10 (at least 10.0.2 but I think 10.0.0) there is Failure and since version 10.2 there is also FailureQ. As often the documentation is somewhat vague and says ”Failure is generated by ... - asked by Albert Retey (12 votes), answered by Leonid Shifrin (9 votes) —————————- [Display grayscale image as 3d plot] http://mathematica.stackexchange.com/questions/127210/display-grayscale-image-as-3d-plot How to build 3d plot of grayscale image where x,y - pixel coordinates, z - pixel intensity? I tried ListPlot3D[ImageData[image]], but ImageData gives just intensities. I suppose a possible solution ... - asked by red1ynx (10 votes), answered by Kuba (11 votes) —————————- [Automatically draw ellipsoids around groups of select points] http://mathematica.stackexchange.com/questions/126899/automatically-draw-ellipsoids-around-groups-of-select-points Suppose you have a ListPlot, and there are certain points you wish to emphasize belong to particular group. I would like to make a function that automatically draws an ellipsoid around a select group ... - asked by SumNeuron (10 votes), answered by Szabolcs (11 votes) —————————- [Enter colors directly into notebook?] http://mathematica.stackexchange.com/questions/127245/enter-colors-directly-into-notebook In Mathematica notebook interface, you can evaluate: In[1]:= Black and you get a colored squared representing the color. Then I can copy and paste this color square and use it as input, like so: ... - asked by becko (9 votes), answered by WReach (10 votes) —————————- [Large Dataset query fails if column contains Missing] http://mathematica.stackexchange.com/questions/126851/large-dataset-query-fails-if-column-contains-missing In version 11.0 (Win 8.1 Pro) a query on a large Dataset for a column that contains Missing fails most unceremoniously. With dsTest = AssociationThread[{"a", "b"}, If[Last@# == 10000, ... - asked by Edmund (9 votes), answered by JasonB (7 votes) ================================== Greatest hits from previous weeks: ================================== [Is there an open source implementation of Mathematica-the-language?] http://mathematica.stackexchange.com/questions/4454/is-there-an-open-source-implementation-of-mathematica-the-language I’ve seen questions before such as ”What is the best open-source equivalent for Mathematica?”, but that speciﬁc question (and that line of inquiry in general) cares more about the computer algebra ... - asked by sblom (81 votes), answered by Simon (63 votes) —————————- [What are the most common pitfalls awaiting new users?] http://mathematica.stackexchange.com/questions/18393/what-are-the-most-common-pitfalls-awaiting-new-users As you may already know, Mathematica is a wonderful piece of software. However, it has a few characteristics that tend to confuse new (and sometimes not-so-new) users. That can be clearly seen from ... - asked by Dr. belisarius (341 votes), answered by Michael E2 (195 votes) ================================== Can you answer these? ================================== [Enable ﬁle completion by default?] http://mathematica.stackexchange.com/questions/127203/enable-file-completion-by-default File completions work for Import and Get but not with &lt;&lt; syntax as you can see: Is there some way to enable this? - asked by M.R. (2 votes) —————————- [Trouble with NIntegrate strategy ”DoubleExponentialOscillatory” when trying to ListPlot the results] http://mathematica.stackexchange.com/questions/126832/trouble-with-nintegrate-strategy-doubleexponentialoscillatory-when-trying-to-l Can someone point me in the right direction? I ’ve been puzzling with this for weeks... I have a huge function (of the form f(y,ξ)sin(ξx) ) to integrate in ξ in region (0, Inﬁnity) and I use ... - asked by George13 (1 vote) —————————- [Using an umlaut for a keyboard shortcut] http://mathematica.stackexchange.com/questions/126909/using-an-umlaut-for-a-keyboard-shortcut How can I deﬁne a keyboard shortcut based on an umlaut like ü? KeyEvent in KeyEventTranslations.tr doesn’t seem to register umlaut based keyboard inputs. For example, after adding ... - asked by Karsten 7. (3 votes) ### 5.15 Tuesday, September 20, 2016 ================================== Top new questions this week: ================================== [The paradigm behind Dynamic and related functionality] http://mathematica.stackexchange.com/questions/126471/the-paradigm-behind-dynamic-and-related-functionality Dynamic and the related functionality strikes me as a very unique way to build quick and dirty personal GUIs which are great for experimentation. I suspect that this is only because of my lack of ... - asked by Szabolcs (24 votes), answered by Leonid Shifrin (21 votes) —————————- [Bug with iterated With: Referring to function arguments invalidates previous deﬁnitions] http://mathematica.stackexchange.com/questions/126425/bug-with-iterated-with-referring-to-function-arguments-invalidates-previous-def G[x_] := With[{a = 0}, With[{b = x}, a]] G @ 0 F[x_] := With[{a = 0}, {b = x}, a] F @ 0 gives 0 a I would expect both to behave exactly the same. It seems that referring to the parameter ... - asked by masterxilo (20 votes), answered by Kuba (20 votes) —————————- [How to quickly ﬁnd all grid cells covered by a geometric region?] http://mathematica.stackexchange.com/questions/126346/how-to-quickly-find-all-grid-cells-covered-by-a-geometric-region I’m trying to compute a complete set of unit grid cells (”pixels”) which a geometric region covers at least partially. I have constructed a method that produces correct results: With[{reg = ... - asked by kirma (14 votes), answered by george2079 (9 votes) —————————- [Cone Trees: map a graph onto geometric shape] http://mathematica.stackexchange.com/questions/126657/cone-trees-map-a-graph-onto-geometric-shape Question Is it possible to map a Graph onto a geometric object such as a Cone? Motivation Visualizing large trees can be tedious, especially when limited to the conﬁnes of the printed page. One ... - asked by SumNeuron (13 votes), answered by Szabolcs (18 votes) —————————- [Evaluate expressions within Vim] http://mathematica.stackexchange.com/questions/126449/evaluate-expressions-within-vim I want to be able to type a quick Mathematica expression, such as 550/3. (e.g. common math), Sum[i, {i, 0, n}]//TeXForm//ToString (e.g. writing LaTeX document), or {55, 1, 10, 40, 9}//Total (e.g. ... - asked by Andrew MacFie (11 votes), answered by Andrew MacFie (11 votes) —————————- [Non newtonian calculus] http://mathematica.stackexchange.com/questions/126730/non-newtonian-calculus I would like to deﬁne a new operator say $$\text {stard}[f[x]] = \lim _{h\rightarrow 0}\left (\frac {f[x+h]}{f[x]}\right )^{\frac {1}{h}}$$ I think it must be done with an upvalue but I do not know how to ... - asked by cyrille.piatecki (10 votes), answered by Szabolcs (18 votes) —————————- [How could I perform Region or Polygon Clipping in mathematica?] http://mathematica.stackexchange.com/questions/126463/how-could-i-perform-region-or-polygon-clipping-in-mathematica I need to clip several regions reg: like Rectangle, Polygon, Ellipse... My goal isn’t to plot the clipping but to have a representation of each new region. I searched if there was any package or ... - asked by A.M. (10 votes), answered by george2079 (4 votes) ================================== Greatest hits from previous weeks: ================================== [Beautiful dance of the Earth and Venus around the sun] http://mathematica.stackexchange.com/questions/115358/beautiful-dance-of-the-earth-and-venus-around-the-sun I have seen very nice dynamic graphics created by users of Ma. I would like to get help whether the following graphics can be created using Ma. I was not able to create the dynamic picture here. ... - asked by ramesh (12 votes), answered by ubpdqn (6 votes) —————————- [How can this image (optical illusion) be created with Mathematica?] http://mathematica.stackexchange.com/questions/24148/how-can-this-image-optical-illusion-be-created-with-mathematica I came across this image the other day: and liked the sensation of it pulsing. I was wondering if anyone would know how to create something similar with Mathematica (without the Pink Floyd Dark ... - asked by Mike Honeychurch (53 votes), answered by halirutan (66 votes) ================================== Can you answer these? ================================== I have a question about subscript policy. For some reason I have some variables called Subscript[q, 1], Subscript[q, 2], Subscript[q, 3] and Subscript[q, 4]. I know that I could have called them in ... - asked by MaPo (1 vote) —————————- [Diﬃcult R installation] http://mathematica.stackexchange.com/questions/126501/difficult-r-installation In RLink and R v3.0.1?, there is an update which say that the problem of the lack of compatibility between the expected version and the last version of R has been settled for version 10.0.1 of ... - asked by cyrille.piatecki (2 votes) —————————- [Does Overﬂow[] poison session for N?] http://mathematica.stackexchange.com/questions/126337/does-overflow-poison-session-for-n Summary: once Mathematica hits an overﬂow error, N[] appears to break for even simple calculations. RealDigits[N[Sqrt[2]-1,10^8]]; I was impressed that Mathematica ran the code above (ﬁrst 100 ... - asked by barrycarter (9 votes) ### 5.16 Tuesday, September 13, 2016 ================================== Top new questions this week: ================================== [Drawing picture with straight line (Petros Vrellis’s Art)] http://mathematica.stackexchange.com/questions/126161/drawing-picture-with-straight-line-petros-vrelliss-art I am trying to extend Writing a word with straight lines for any picture/image. I guess the basic idea is to ﬁnd a set of points in the image region and then draw random lines through them. Let’s ... - asked by Sumit (16 votes), answered by Rahul (6 votes) —————————- [How do I count the most used functions across a set of notebooks?] http://mathematica.stackexchange.com/questions/125960/how-do-i-count-the-most-used-functions-across-a-set-of-notebooks WolframLanguageData allows us to view the most used functions across several code bases like Wolfram Alpha, the documentation, or Stack Exchange. I was curious about the results for my own collection ... - asked by Michael Hale (15 votes), answered by Michael Hale (11 votes) —————————- [How to ReplaceAll except within speciﬁed heads] http://mathematica.stackexchange.com/questions/125918/how-to-replaceall-except-within-specified-heads ReplaceAll[expr, rule] and ReplaceRepeated[expr, rule] search through all subexpressions of expr applying rule where they match. Are there built-in Mathematica functions that do the same thing, ... - asked by QuantumDot (15 votes), answered by JHM (15 votes) —————————- [Is this a bug in Replace?] http://mathematica.stackexchange.com/questions/125771/is-this-a-bug-in-replace Consider the following minimal examples. This one works as expected, replacing trees starting from the inside with a numerical value. ClearAll[tree]; x = tree["A", {tree["B", {1, 2}], 3}]; Replace[x, ... - asked by István Zachar (14 votes), answered by Leonid Shifrin (17 votes) —————————- [How do I test if a variable represents a sequence?] http://mathematica.stackexchange.com/questions/126193/how-do-i-test-if-a-variable-represents-a-sequence I created a variable that represents a sequence: mySeq = Sequence[1, 2, 3]; I wanted to use that variable as an argument for some functions. But I got in trouble. For example, FreeQ[mySeq, 1] ... - asked by Fernando Saldanha (12 votes), answered by Edmund (8 votes) —————————- [How to calculate the numerical integral more eﬃciently?] http://mathematica.stackexchange.com/questions/126001/how-to-calculate-the-numerical-integral-more-efficiently Rencently, I ecountered the following numerical intergral: \begin{cases} \mathbf I_1=\displaystyle \int_{t}\mathbf N' {\mathbf N'}^{\text T}{\rm d}t\\ \mathbf I_2=\displaystyle \int_{t}\mathbf N'' - asked by Shutao Tang (11 votes), answered by Anton Antonov (8 votes) —————————- [Optional argument that can be completely omitted?] http://mathematica.stackexchange.com/questions/125929/optional-argument-that-can-be-completely-omitted I am writing a simple function return similar words. Clear[similarWords] similarWords[string_]:=Nearest[WordList[],string] I want to add another argument n which is optional. When it presents, it ... - asked by matheorem (11 votes), answered by Szabolcs (12 votes) ================================== Greatest hits from previous weeks: ================================== [Writing a word with straight lines] http://mathematica.stackexchange.com/questions/113403/writing-a-word-with-straight-lines Here is an interesting way to write a word: (it is from a poster for the International Museum Day 2006; I believe it even won an award at an international design competition) by Boris Ljubicic. ... - asked by VividD (71 votes), answered by Anton Antonov (32 votes) —————————- [Exporting graphics to PDF - huge ﬁle] http://mathematica.stackexchange.com/questions/1542/exporting-graphics-to-pdf-huge-file I want to draw some basic surfaces, export them to PDF and include them in a LaTeX ﬁle. I create a simple 3D graphics object, for instance with  ParametricPlot3D[{r Cos[\[Theta]], r Sin[\[Theta]], ... - asked by Matthew Leingang (85 votes), answered by Heike (73 votes) ================================== Can you answer these? ================================== [Finding covariation between datasets] http://mathematica.stackexchange.com/questions/125963/finding-covariation-between-datasets For me this is a very fascinating problem, which I however lack the ability to deal with as well as the nomenclature to describe properly. (Please feel free to edit the title). The conditions are the ... - asked by MathLind (2 votes) —————————- [Wolfram math on windows using PBSPro cluster] http://mathematica.stackexchange.com/questions/125861/wolfram-math-on-windows-using-pbspro-cluster A user wishes to use math application running on our PBSPpro cluster. Our cluster is accessible to linux users, running qsub to submit their jobs. We have math10.4 for our cluster users, with ... - asked by Dvory (2 votes) —————————- [Unexpected view of a vectorial triad in a combination of a Plot3D with Graphics3D] http://mathematica.stackexchange.com/questions/126168/unexpected-view-of-a-vectorial-triad-in-a-combination-of-a-plot3d-with-graphics3 I am preparing an illustration for the lecture on diﬀerential geometry. In this demonstration I am illustrating the Monge parameterization of the surface: R = {xx, yy, 55 + xx^2 - xx^3 - 2*yy^2}; (* ... - asked by Alexei Boulbitch (2 votes) ### 5.17 Tuesday, September 6, 2016 ================================== Top new questions this week: ================================== [The Game of Hex in Mathematica] http://mathematica.stackexchange.com/questions/125460/the-game-of-hex-in-mathematica The Game of Hex is a game originally developed by Nash, and it’s rules are very simple. You start out with a hexagonal tiling of some size: There are two players. The game is in turns, and every ... - asked by TreFox (31 votes), answered by C. E. (26 votes) —————————- [Visualize fraction] http://mathematica.stackexchange.com/questions/125209/visualize-fraction I would like to visualize a fraction like the square root of 2 with Mathematica. I found this visualization of Pi in the internet and wonder how this would be done with Mathematica. The image shows ... - asked by Arjihad (22 votes), answered by Kuba (20 votes) —————————- [Monad-like structures in Mathematica] http://mathematica.stackexchange.com/questions/125537/monad-like-structures-in-mathematica I have been trying to code monad-like structures in Mathematica. However, I am facing some issues and I was wondering if anyone can help. I will give some background in the hope it can be useful to ... - asked by Diogo Gomes (16 votes), answered by m_goldberg (6 votes) —————————- [paclets updating awareness and tracking] http://mathematica.stackexchange.com/questions/125199/paclets-updating-awareness-and-tracking It turns out that some silent updating may be done in our computers with paclets. See for example here. How are we aware that something has been changed ? Can we track updating/versions of paclets ? ... - asked by andre (16 votes) —————————- [Is it important that the front-end has a built-in parser?] http://mathematica.stackexchange.com/questions/125180/is-it-important-that-the-front-end-has-a-built-in-parser The Notebook interface has a parser that seems aware of all operator-precedences, allowing us to step through the expressions (rather: Box-) hierarchy with Ctrl+. This is extremely convenient, saving ... - asked by masterxilo (15 votes), answered by John Fultz (18 votes) —————————- [Package organization] http://mathematica.stackexchange.com/questions/125579/package-organization When writing a Mathematica package Foo, with functions f1, f2 and f3, one can use the template: BeginPackage["Foo"]; f1::usage = "f1[] ...."; f2::usage = "f2[] ...."; Begin["Private"]; f1[]:= ... - asked by Pixor (14 votes), answered by Szabolcs (17 votes) —————————- [ClearAll::clloc - ”Cannot clear local variable x” in Block[x, ...] - why?] http://mathematica.stackexchange.com/questions/125251/clearallclloc-cannot-clear-local-variable-x-in-blockx-why Block[{x}, ClearAll@x] ClearAll::clloc: Cannot clear local variable x. The documentation just says An error occurs because ClearAll cannot be used with a local variable in Block: and ... - asked by masterxilo (14 votes) ================================== Greatest hits from previous weeks: ================================== [Beautiful dance of the Earth and Venus around the sun] http://mathematica.stackexchange.com/questions/115358/beautiful-dance-of-the-earth-and-venus-around-the-sun I have seen very nice dynamic graphics created by users of Ma. I would like to get help whether the following graphics can be created using Ma. I was not able to create the dynamic picture here. ... - asked by ramesh (11 votes), answered by ubpdqn (6 votes) —————————- [How can I draw the Olympic rings with Mathematica?] http://mathematica.stackexchange.com/questions/8885/how-can-i-draw-the-olympic-rings-with-mathematica How can I draw the 5 interlocking Olympic rings with Mathematica? (SVG version) Edit Hard choice, but some pretty cool answers here. I didn’t have 3D answers in mind when I posted the question, ... - asked by Mike Honeychurch (41 votes), answered by cormullion (18 votes) ================================== Can you answer these? ================================== [Creating notebooks with speciﬁc options being editable but not saveable] http://mathematica.stackexchange.com/questions/125676/creating-notebooks-with-specific-options-being-editable-but-not-saveable The goal is to create a notebook whose options, when the notebook is opened, are ﬁxed regardless of edits done to the notebook. E.g. WindowSize -&gt; Automatic and WindowMargins -&gt; 30 should be ... - asked by Kuba (8 votes) —————————- [Possible bug with Dataset formatting for incompatible shapes and Missing] http://mathematica.stackexchange.com/questions/125689/possible-bug-with-dataset-formatting-for-incompatible-shapes-and-missing Bug introduced in 11.0.0 The problem: {&lt;|"a" -&gt; Range[5]|&gt;, &lt;|"a" -&gt; Missing["KeyAbsent", "a"]|&gt;} // Dataset More detailed example shows that 5 is the magic number and ... - asked by Kuba (10 votes) —————————- [TensorContract applied twice] http://mathematica.stackexchange.com/questions/125588/tensorcontract-applied-twice I have a very simple question about TensorContract command: I’m declaring Assumptions = {T \[Element] Arrays[{4, 4, 4, 4}], a \[Element] Arrays[{4, 4}], b \[Element] Arrays[{4, 4}]}; so T is a ... - asked by MaPo (3 votes) ### 5.18 Tuesday, August 30, 2016 ================================== Top new questions this week: ================================== [How to make a Spherical Cow?] http://mathematica.stackexchange.com/questions/125043/how-to-make-a-spherical-cow Being a theoretical physicist, I always have a great respect for Spherical Cow. So I thought about making one myself. I am not sure how can I create (something considered to be the simplest!) this ... - asked by Sumit (29 votes), answered by andre (41 votes) —————————- [Unit Discovery: Is this some sort of a sick joke?] http://mathematica.stackexchange.com/questions/124745/unit-discovery-is-this-some-sort-of-a-sick-joke Alright, let’s have some fun here. I am essentially following the documentation by Wolfram, just looking at diﬀerent quantities. N[UnitConvert[Quantity["earth's gravity"]]] 9.80665m/(s)^2 Hmm, ... - asked by Pirx (26 votes), answered by Xavier (27 votes) —————————- [Remove noise from data] http://mathematica.stackexchange.com/questions/124928/remove-noise-from-data Hi, as you can see above I have some experimental data which has a large oﬀset and shows clear noise ﬂuctations around the tendency of the curve. I wanted to ask if someone could suggest me a ... - asked by Filipe (23 votes), answered by nikie (22 votes) —————————- [Q&A Mathematica v.11 Neural Networks: A comprehensive look at Layers, Net Functions, and pioneering into this [[experimental]] code] http://mathematica.stackexchange.com/questions/124977/qa-mathematica-v-11-neural-networks-a-comprehensive-look-at-layers-net-functi Motivation As Mathematica v.11 was released earlier this month with a host of new [[experimental]] functions and a limited number of examples on curated data that do not cover all layers, options, ... - asked by SumNeuron (20 votes), answered by Sebastian (12 votes) —————————- [Custom OpenerView with lazy evaluation] http://mathematica.stackexchange.com/questions/124892/custom-openerview-with-lazy-evaluation OpenerView can be nested to create a hierarchical structure such as this: One great aspect is that it remembers which lists are open and which are closed even after the parent has been closed and ... - asked by C. E. (16 votes), answered by C. E. (7 votes) —————————- [RNN in Mathematica?] http://mathematica.stackexchange.com/questions/124988/rnn-in-mathematica Recurrent neural network is an important part of machine learning and its improved version: LSTM network is widely applied, but Mathematica seemingly is in lack of these two features and in my ... - asked by Wjx (15 votes), answered by Taliesin Beynon (19 votes) —————————- [Pentagonal spiral in Mathematica] http://mathematica.stackexchange.com/questions/125007/pentagonal-spiral-in-mathematica I would like to plot an image of what I call a pentagonal spiral with Mathematica. A sample image of what I’d like to obtain is this (sorry for low-quality): My initial idea was to get some kind of ... - asked by bharb (14 votes), answered by Wjx (11 votes) ================================== Greatest hits from previous weeks: ================================== [Labeling individual curves in Mathematica] http://mathematica.stackexchange.com/questions/4444/labeling-individual-curves-in-mathematica I need to create a plot for export and inclusion in a report. Is there a better way to label curves than PlotLegends? From what I’ve read and my personal experience, PlotLegends is pretty bad. Is ... - asked by Tianxiang Xiong (44 votes), answered by Artes (37 votes) —————————- [How to make this beautiful animation] http://mathematica.stackexchange.com/questions/112700/how-to-make-this-beautiful-animation How to make an animation of following gif in Mathematica? Edit: The animation shown above was created by Charlie Deck in processing. And how to make 3D analog? I tried ﬁrst few steps line = ... - asked by vito (45 votes), answered by C. E. (48 votes) ================================== Can you answer these? ================================== [WolframScript never exits (v11 only)] http://mathematica.stackexchange.com/questions/124667/wolframscript-never-exits-v11-only after updating to version 11, I came across a problem with the execution of package ﬁles via bash. The WolframScript program runs the entire code, but frequently it does not exit properly and as a ... - asked by fabio.hipolito (5 votes) —————————- [Representing inequalties with proper boundaries] http://mathematica.stackexchange.com/questions/124747/representing-inequalties-with-proper-boundaries I have a very simple problem: given an inequality, I’d like to represent it in a regional plot marking the boundary diﬀerently depending whether it belongs to the region or not. For example I’d like ... - asked by Geon (3 votes) —————————- [StringTemplate performance issue] http://mathematica.stackexchange.com/questions/125087/stringtemplate-performance-issue StringTemplate introduced in version 10 is very convenient in constructing formatted data. However, it seems to have a huge performance issue. Consider this example: data = RandomInteger[1, 100, ... - asked by xslittlegrass (5 votes) ### 5.19 Tuesday, August 23, 2016 ================================== Top new questions this week: ================================== [GeoPosition coordinates from Shape ﬁle (.SHP) with unknown Datum] http://mathematica.stackexchange.com/questions/124121/geoposition-coordinates-from-shape-file-shp-with-unknown-datum The City of Amsterdam supports an Open Data policy. Much information can be retrieved at the level of boroughs (stadsdelen). Unfortunately, GeoGraphics does not provide outlines of these smaller ... - asked by Romke Bontekoe (12 votes), answered by JasonB (8 votes) —————————- [Detecting collisions in FEM] http://mathematica.stackexchange.com/questions/124324/detecting-collisions-in-fem Say I want to study the deformation of a pitchfork when you have it ﬁxed on the bottom and push one side. &lt;&lt; NDSolveFEM Ω = RegionDifference[Cuboid[{0, -5}, {1, 0}], Cuboid[{0.45, ... - asked by tsuresuregusa (12 votes) —————————- [Discovering crosswords] http://mathematica.stackexchange.com/questions/124552/discovering-crosswords I am trying to create a code that can identify the following terms: MATHEMATICA, STACK, EXCHANGE and USERS. list1={"M","S","T","A","S","I","S","X","X","T","R","X"}; list2={"A ","T ","H ","X ","R ","X ... - asked by Leandro Maciel de Carvalho (11 votes), answered by C. E. (15 votes) —————————- [29 Diﬀerential equations hang/not solved in version 11 compared to 10.4, looking for cause] http://mathematica.stackexchange.com/questions/124573/29-differential-equations-hang-not-solved-in-version-11-compared-to-10-4-lookin I run Kamke diﬀerential equations in version 11 and compared the result to version 10.4. Found 29 diﬀerential equations that are no longer solved in version 11. Actually v11 hangs on these, eating ... - asked by Nasser (11 votes) —————————- [Using predeﬁned expressions as free variables in a pure function] http://mathematica.stackexchange.com/questions/124530/using-predefined-expressions-as-free-variables-in-a-pure-function I want to have a function value of an expression where some variables are solutions to some set of equations, with some values of parameters. I had an idea to use pure functions for that. However, ... - asked by Picek (10 votes), answered by Alexey Popkov (4 votes) —————————- [How to delete unnecessary resistances in a resistance network] http://mathematica.stackexchange.com/questions/124475/how-to-delete-unnecessary-resistances-in-a-resistance-network I’m still dealing with resistance network processing and got one problem left: how to delete unnecessary resistances? Background Let’s assume we are junior high students and know nothing about ... - asked by Wjx (10 votes), answered by Sascha (5 votes) —————————- [Object detection in a low contrast image] http://mathematica.stackexchange.com/questions/124060/object-detection-in-a-low-contrast-image I have a small dark object in the upper left corner of an image. How can I separate it from the noisy rest and determine its IntensityCentroid? The problem is that the objects intensity is not ... - asked by mrz (10 votes), answered by Svyatoslav Korneev (12 votes) ================================== Greatest hits from previous weeks: ================================== [Make a beautiful Moiré eﬀect] http://mathematica.stackexchange.com/questions/112998/make-a-beautiful-moir%c3%a9-effect How do I make the following Moiré pattern? I tried: A = Plot[Table[n, {n, 1, 30}], {x, 0, 31}, GridLines -&gt; {Table[n, {n, 1, 30}], None}, GridLinesStyle -&gt; AbsoluteThickness[1.2], ... - asked by vito (23 votes), answered by gpap (34 votes) —————————- [Beautiful dance of the Earth and Venus around the sun] http://mathematica.stackexchange.com/questions/115358/beautiful-dance-of-the-earth-and-venus-around-the-sun I have seen very nice dynamic graphics created by users of Ma. I would like to get help whether the following graphics can be created using Ma. I was not able to create the dynamic picture here. ... - asked by ramesh (11 votes), answered by ubpdqn (6 votes) ================================== Can you answer these? ================================== [CapForm bugged in V11?] http://mathematica.stackexchange.com/questions/124591/capform-bugged-in-v11 It appears on my system (OSX 10.10.5) that CapForm isn’t behaving itself in V11. Initially I thought it was a problem with the combination of CapForm and VertexColors but it seems even weirder than ... - asked by Quantum_Oli (6 votes) —————————- [Linear tangent steering law and orbital insertion altitude] http://mathematica.stackexchange.com/questions/124489/linear-tangent-steering-law-and-orbital-insertion-altitude I’ve been trying to ﬁgure out how to build a rocket launch simulation that allows the user to specify the desired altitude at which a payload will be inserted into a stable circular orbit, but have ... - asked by AlexR (2 votes) —————————- [What is a ”generic case”?] http://mathematica.stackexchange.com/questions/124347/what-is-a-generic-case Introduction With this question I am coming back to a long-standing issue I have with Mma’s concept of a ”generically correct” result. The basic idea seems to be, vaguely, that if a result is true in ... - asked by Pirx (6 votes) ### 5.20 Tuesday, August 16, 2016 ================================== Top new questions this week: ================================== [Can Mathematica put these puzzle pieces together?] http://mathematica.stackexchange.com/questions/123993/can-mathematica-put-these-puzzle-pieces-together I have ﬁve DXF ﬁles with various geometric ﬁgures. Are squares with a diﬀerent geometric shape in each DXF ﬁle... Four DXF ﬁles have a square with a diﬀerent geometric shape on one side ... - asked by Leandro Maciel de Carvalho (17 votes), answered by kirma (11 votes) —————————- [How to monitor the process of Neural Network Learning] http://mathematica.stackexchange.com/questions/123684/how-to-monitor-the-process-of-neural-network-learning Main Problem I’m exploring the neural network in v11 and I would like to monitor the training progress in my own way instead of Mathematica’s default way. So my question is, how to do this ... - asked by Wjx (17 votes), answered by Taliesin Beynon (13 votes) —————————- [Changes to Coeﬃcient function in v10.2] http://mathematica.stackexchange.com/questions/123565/changes-to-coefficient-function-in-v10-2 In the version Mathemaica 10.4, I am very surprised that the core function Coeﬃcient has changed, e.g., Coefficient[3 x x + 8 y y - 24 x y, 2 x y] 0 In previous versions (e.g. v9.0.1, ... - asked by Orders (17 votes) —————————- [Unexpected behaviour from Table[]] http://mathematica.stackexchange.com/questions/124046/unexpected-behaviour-from-table The following code in Mathematica 11: iList = {i, -10, 10, 2}; Table[i, iList] produces this result: {i, i, i, i} Where in version 10 (and presumably earlier versions) it produced an error: ... - asked by Bruce Crawford (16 votes), answered by Szabolcs (15 votes) —————————- [Can Mathematica act like a web server?] http://mathematica.stackexchange.com/questions/123805/can-mathematica-act-like-a-web-server I have a Mathematica program that modiﬁes images that I would like to make available for other people to use through the web. The input is only one parameter. So, for example, I could run it as a ... - asked by Tyler Durden (16 votes) —————————- [How to generate all possible orderless partitions of a list according to another list?] http://mathematica.stackexchange.com/questions/123835/how-to-generate-all-possible-orderless-partitions-of-a-list-according-to-another This question is hard to describe in plain text. So I will post an example and a working code (brute force) to illustrate. For example I have a list: {1, 2, 3, 4, 5} and a partition list {2, 2, 1}. I ... - asked by happy ﬁsh (15 votes), answered by Mr.Wizard (11 votes) —————————- [RandomPoint crashes kernel] http://mathematica.stackexchange.com/questions/123735/randompoint-crashes-kernel Bug introduced in Version 11.0 Reported as CASE:3686963, 12 Aug 2016 I attempted to determine whether the problem with RandomPoint identiﬁed in my answer to question 89384 had been ﬁxed in ... - asked by bbgodfrey (12 votes), answered by ilian (6 votes) ================================== Greatest hits from previous weeks: ================================== [How to Plot an Inﬁnite Series] http://mathematica.stackexchange.com/questions/14083/how-to-plot-an-infinite-series I want to sketch the graphs of for $$t=0, 0.01, 0.1, 0.5, 1, 10$$ on the same axes. For $$t=0$$, I input Plot[{1/2 + ... - asked by Vladimir (2 votes), answered by chris (9 votes) —————————- [How to make this beautiful animation] http://mathematica.stackexchange.com/questions/112700/how-to-make-this-beautiful-animation How to make an animation of following gif in Mathematica? Edit: The animation shown above was created by Charlie Deck in processing. And how to make 3D analog? I tried ﬁrst few steps line = ... - asked by vito (45 votes), answered by C. E. (48 votes) ================================== Can you answer these? ================================== I wanted to print out the holidays in Germany in 2016: DayRange[DateObject[{2016, 1, 1}], DateObject[{2016, 12, 31}], "Holiday", HolidayCalendar -&gt; {"Germany", "Bavaria"}] The result list ... - asked by mrz (2 votes) —————————- [How to crawl some website needed username and password] http://mathematica.stackexchange.com/questions/123771/how-to-crawl-some-website-needed-username-and-password In version 11,if we want to crawl public website like wiki,we can do it like this: URLRead["https://en.wikipedia.org/wiki/Wiki", "Body"] But I don’t know how to crawl some website needed ... - asked by yode (4 votes) —————————- [NFourierTransform of an interpolating function] http://mathematica.stackexchange.com/questions/123800/nfouriertransform-of-an-interpolating-function I have an interpolating function called rs22 - a solution from NDSolve - which is deﬁned from 0 to about 1 ms. rs22 is a function that reaches a non-zero equilibrium value. (only shown here up to ... - asked by Shiki (3 votes) ### 5.21 Tuesday, August 9, 2016 ================================== Top new questions this week: ================================== [PostScript-like drawing in Mathematica?] http://mathematica.stackexchange.com/questions/123289/postscript-like-drawing-in-mathematica To illustrate by example, construct an equilateral triangle in PostScript: 0 0 moveto %moveto origin 6 0 lineto %construct first line segment 6 0 translate %translate ... - asked by Alan (14 votes), answered by WReach (21 votes) —————————- [Eﬃciently exchange elements between two lists] http://mathematica.stackexchange.com/questions/123221/efficiently-exchange-elements-between-two-lists I have two lists with equal length, and I want to exchange the elements on every even positions. For example, {{1, 2, 3, 4, 5}, {6, 7, 8, 9, 10}} will return {{1, 7, 3, 9, 5}, {6, 2, 8, 4, 10}} ... - asked by happy ﬁsh (13 votes), answered by Kuba (12 votes) —————————- [Finite element simulation of Airy waves] http://mathematica.stackexchange.com/questions/122063/finite-element-simulation-of-airy-waves I am attempting to solve for waves on a water surface starting with a two dimensional solution. The equations are that the water must satisfy Laplace’s equation everywhere with a time dependent ... - asked by Hugh (13 votes), answered by user21 (10 votes) —————————- [How do you make a Neural Net?] http://mathematica.stackexchange.com/questions/123458/how-do-you-make-a-neural-net In the new Mathematica release (v11), NeuralNetworks is one of the new main features. However, the documentation isn’t that clear on what function should be used in a Net. The documentation on ... - asked by JHM (12 votes), answered by Searke (13 votes) —————————- [How to plot data by counties?] http://mathematica.stackexchange.com/questions/123324/how-to-plot-data-by-counties I’d like to plot county data as in this D3 example: Is there a way to do this with GeoGraphics, or at least to get path polygons per county and then plot them with diﬀerent colors? The ﬁrst ... - asked by M.R. (11 votes), answered by C. E. (9 votes) —————————- [Why are delayed deﬁnitions in scoping functions NOT documented?] http://mathematica.stackexchange.com/questions/122061/why-are-delayed-definitions-in-scoping-functions-not-documented As outlined here, := may be used in scoping constructs like With to give delayed deﬁnitions, but this is undocumented. This has been in the language since at least Mathematica 4.0. It is very ... - asked by Mr.Wizard (11 votes) —————————- [Shading under a curve with dots]http://mathematica.stackexchange.com/questions/123422/shading-under-a-curve-with-dots I plotted the function $$y=x^2$$ using the Plot command Plot[x^2, {x,-5,5}] I need to shade the area under the curve using a pattern (dots pattern), not using a solid color or a hue. Is it possible? ... - asked by James (10 votes), answered by JasonB (14 votes) ================================== Greatest hits from previous weeks: ================================== [General strategies to write big code in Mathematica?] http://mathematica.stackexchange.com/questions/109888/general-strategies-to-write-big-code-in-mathematica I think after six months of exposure to Mathematica and the Wolfram Language I am fairly OK with writing short codes and snippets. However, what are some general strategies to use in order to write ... - asked by Ali Hashmi (94 votes), answered by Leonid Shifrin (75 votes) —————————- [Where can I ﬁnd examples of good Mathematica programming practice?] http://mathematica.stackexchange.com/questions/18/where-can-i-find-examples-of-good-mathematica-programming-practice I consider myself a pretty good Mathematica programmer, but I’m always looking out for ways to either improve my way of doing things in Mathematica, or to see if there’s something nifty that I haven’t ... - asked by J. M. (430 votes), answered by faysou (388 votes) ================================== Can you answer these? ================================== [Can I use Mathematica as a constraint solver?] http://mathematica.stackexchange.com/questions/123487/can-i-use-mathematica-as-a-constraint-solver I have been using SMT solvers for program analysis. Basically the idea is to translate x86 assembly code to SMT formulas and use the solver for automatic input test generation. There is a Microsoft ... - asked by Edgar (1 vote) —————————- [Why is this function slower after a simple change?] http://mathematica.stackexchange.com/questions/122109/why-is-this-function-slower-after-a-simple-change I have a function that calculates the rank of a restricted growth string deﬁned like so, rankKRGS[{}] = 0; rankKRGS[string_] := With[{n = Length@string, k = Max@string + 1, alone = ... - asked by Jordy Dickinson (3 votes) —————————- [Is there an eﬃcient way to monitor the progress of a task remotely?] http://mathematica.stackexchange.com/questions/123181/is-there-an-efficient-way-to-monitor-the-progress-of-a-task-remotely Recently, I’ve been running Mathematica packages on a remote cluster using SSH (using, e.g. the command nohup nice math -noprompt -run "&lt;&lt;myPackage.m" &gt; myOutput &amp; so that the output ... - asked by Nikhil Anand (2 votes) ### 5.22 Tuesday, August 2, 2016 ================================== Top new questions this week: ================================== [How can I detect locations of Go (aka Baduk, Weiqi) stones on a board?] http://mathematica.stackexchange.com/questions/121835/how-can-i-detect-locations-of-go-aka-baduk-weiqi-stones-on-a-board The Goal There are a couple apps that score a Go board from a photo. I was wondering if something like that would be possible with Mathematica. The key step is to detect the positions of the stones ... - asked by Mark S. (19 votes), answered by halirutan (2 votes) —————————- [What are all the ”magic” Symbols in the Mathematica language?] http://mathematica.stackexchange.com/questions/121981/what-are-all-the-magic-symbols-in-the-mathematica-language Leonid Shifrin once wrote (excerpted): (Unevaluated) is one of a very few ”magic symbols”, along with Sequence and Evaluate - these are deeply wired into the system and can not be easily ... - asked by Mr.Wizard (16 votes), answered by Mr.Wizard (9 votes) —————————- [What has changed in pattern matching functions with the Orderless attribute?] http://mathematica.stackexchange.com/questions/121564/what-has-changed-in-pattern-matching-functions-with-the-orderless-attribute In making an attempt to answer this question, we ran into a version-dependent pattern-matching issue. An extended discussion in the comments transpired, and some inconsistencies arose. Consider the ... - asked by march (16 votes) —————————- [Converting a Sierpinski tetrahedron to a Graph] http://mathematica.stackexchange.com/questions/121553/converting-a-sierpinski-tetrahedron-to-a-graph I need a representation of a 3D Sierpinski gasket as a graph to perform some simulations on. The 2D version is included in GraphData[], but the 3D one is nowhere to be found, so I was wondering if ... - asked by FEARxxx (13 votes), answered by J. M. (2 votes) —————————- [Working with DynamicModule: SetDelayed + OwnValues] http://mathematica.stackexchange.com/questions/121584/working-with-dynamicmodule-setdelayed-ownvalues Shortly, definitions in form of e.g. x:= RandomReal[] have to be avoided inside DynamicModule[{x}, ...]. Why?, this Prints immediately: DynamicModule[{x}, x := Print[1]; {}] It hit us hard in the ... - asked by Kuba (12 votes), answered by Kuba (13 votes) —————————- [How to speed up pattern matching] http://mathematica.stackexchange.com/questions/121911/how-to-speed-up-pattern-matching Main Problem Mr.Wizard posed this question when discussing another problem. I reproduce the main part of Mr.Wizard’s problem here: MatchQ[{1, 2, 3, 4, 5}, {x__?((Echo[##]; False) &amp;), y__}] On ... - asked by Wjx (11 votes), answered by Michael E2 (5 votes) —————————- [How to eﬃciently implement k-FN (k-Furthest Neighbors)?] http://mathematica.stackexchange.com/questions/121541/how-to-efficiently-implement-k-fn-k-furthest-neighbors I’d like to pick k points from a set of points in n-dimensions that are approximately ”maximally apart” (sum of pairwise distances is almost maxed). What is an eﬃcient way to do this in MMA? Using ... - asked by M.R. (10 votes), answered by C. Woods (2 votes) ================================== Greatest hits from previous weeks: ================================== [Writing a word with straight lines] http://mathematica.stackexchange.com/questions/113403/writing-a-word-with-straight-lines Here is an interesting way to write a word: (it is from a poster for the International Museum Day 2006; I believe it even won an award at an international design competition) by Boris Ljubicic. ... - asked by VividD (70 votes), answered by Anton Antonov (32 votes) —————————- [Make a beautiful Moiré eﬀect] http://mathematica.stackexchange.com/questions/112998/make-a-beautiful-moir%c3%a9-effect How do I make the following Moiré pattern? I tried: A = Plot[Table[n, {n, 1, 30}], {x, 0, 31}, GridLines -&gt; {Table[n, {n, 1, 30}], None}, GridLinesStyle -&gt; AbsoluteThickness[1.2], ... - asked by vito (23 votes), answered by gpap (34 votes) ================================== Can you answer these? ================================== [Looking for a package for ﬁnite mappings] http://mathematica.stackexchange.com/questions/121776/looking-for-a-package-for-finite-mappings I am looking for a package for dealing with ”mappings” $$f\colon A\to B$$ where $$A$$ and $$B$$ are ﬁnite subsets of the set of all possible (inert) expressions. I need operations like: Computing $$f(a)$$ ... - asked by masterxilo (3 votes) —————————- [Using Palettes in Mathematica Online] http://mathematica.stackexchange.com/questions/121935/using-palettes-in-mathematica-online my student is using the online version of Mathematica for my class; it appears to not have a palette feature for typing formatted input? This was kind of shocking to me; why wouldn’t there be a ... - asked by Jake Mirra (1 vote) —————————- [Derivation of an interpolation function with multiple arguments] http://mathematica.stackexchange.com/questions/121599/derivation-of-an-interpolation-function-with-multiple-arguments I have the following interpolation function: f[x_,a_,b_]:=70 s[a,b][[1,1,2]][x] where s[a,b] is the solution of a differential equation. s[a_, b_] := NDSolve[{ H2[x] == Rx[x]^2 + G[x, a, b], ... - asked by Maria (2 votes) ### 5.23 Tuesday, July 26, 2016 ================================== Top new questions this week: ================================== [Generate a certain colorful triangle] http://mathematica.stackexchange.com/questions/121353/generate-a-certain-colorful-triangle I want to get a colorful triangle like this: I hope to get a triangle with any number of layers. This is my current method. Actually, I’m not very content with these graph theory functions, since ... - asked by yode (13 votes), answered by Mr.Wizard (7 votes) —————————- [Bad interaction between Join and ListPlot (or Plot)] http://mathematica.stackexchange.com/questions/121289/bad-interaction-between-join-and-listplot-or-plot When you write this code: tab = {{1, 1}}; tab = Join[tab, {{2,2}}]; you expect to get the following table: {{1, 1}, {2, 2}} but, if you write the following code instead: tab = {{1, 1}}; tab = ... - asked by Francisco (11 votes), answered by C. E. (8 votes) —————————- [Handwriting recognition with Mathematica] http://mathematica.stackexchange.com/questions/121051/handwriting-recognition-with-mathematica I am trying to teach Mathematica to read my handwriting. Since I don’t want to ruin my reputation by showing my own handwriting, I am going to use a font called blackjack. Lets say this is a ... - asked by Sumit (11 votes) —————————- [Can one eﬀectively edit a Front End Resource that is already loaded?] http://mathematica.stackexchange.com/questions/121059/can-one-effectively-edit-a-front-end-resource-that-is-already-loaded A number of special deﬁnitions are loaded from .tr ﬁles on Front End initialization and are accessible via FrontEndResource. These are used among other things for various menus and toolsbars, e.g.: - asked by Mr.Wizard (11 votes) —————————- [Bug with Compile and Log2?] http://mathematica.stackexchange.com/questions/121336/bug-with-compile-and-log2 It seems that Log2 in Compile gives numerical errors (CompiledFunction::cfn) if the input is not a power of 2. For instance: test1 = Compile[{{in, _Integer}}, Log2[in]]; test1[3] gives an error ... - asked by JHM (10 votes), answered by Michael E2 (4 votes) —————————- [What is the eﬀect of giving ColorFunctionScaling a numerical argument?] http://mathematica.stackexchange.com/questions/121231/what-is-the-effect-of-giving-colorfunctionscaling-a-numerical-argument (by making a mistake) I realised that ColorFunctionScaling can take a list of numerical arguments rather than just booleans. The following is true for ContourPlot and DensityPlot but not Plot3D and ... - asked by gpap (10 votes), answered by Mr.Wizard (4 votes) —————————- [Reproducing the xkcd ”Self-Description” comic] http://mathematica.stackexchange.com/questions/121160/reproducing-the-xkcd-self-description-comic Trying to brush up on my programming, I wanted to see if I can reproduce at least the ﬁrst two panels of the following comic in Mathematica: I have some code for trying to reproduce the ﬁrst ... - asked by Mayumi Itō (10 votes), answered by Alexey Popkov (7 votes) ================================== Greatest hits from previous weeks: ================================== [Exporting graphics to PDF - huge ﬁle] http://mathematica.stackexchange.com/questions/1542/exporting-graphics-to-pdf-huge-file I want to draw some basic surfaces, export them to PDF and include them in a LaTeX ﬁle. I create a simple 3D graphics object, for instance with  ParametricPlot3D[{r Cos[\[Theta]], r Sin[\[Theta]], ... - asked by Matthew Leingang (84 votes), answered by Heike (71 votes) —————————- [Calculate the 2D Fourier transform of an Image] http://mathematica.stackexchange.com/questions/29203/calculate-the-2d-fourier-transform-of-an-image I am new to Mathematica, and using version 8.0. I would like to calculate the 2D Fourier Transform of an Image with Mathematica and plot the magnitude and phase spectrum, as well as reconstruct the ... - asked by user8727 (2 votes), answered by Nasser (22 votes) ================================== Can you answer these? ================================== [single slit diﬀraction numerical simulation] http://mathematica.stackexchange.com/questions/121474/single-slit-diffraction-numerical-simulation I’m trying to simulate the Fraunhoﬀer diﬀraction at slits(single,double,triple) with Mathematica. In the picture, the red one is analytical result and the green one is numerical result. The ... - asked by Taeshin Kim (5 votes) —————————- [How does the Contours-¿f_1, g1, f_2, g_2,... setting work?] http://mathematica.stackexchange.com/questions/121205/how-does-the-contours%e2%86%92f-1-g1-f-2-g-2-setting-work I want to plot some wavefronts in Mathematica, and I’m having some trouble reining in one of the options for my ContourPlot3D. More speciﬁcally, the documentation for ContourPlot3D says that the ... - asked by Emilio Pisanty (5 votes) —————————- [Is every menu command equivalent to a command that can be executed within a notebook?] http://mathematica.stackexchange.com/questions/121453/is-every-menu-command-equivalent-to-a-command-that-can-be-executed-within-a-note If so, is there a directory which gives the in-notebook command associated with each menu command ? In particular, I would like to know how to replicate the menu command Evaluation -> Quit Kernel -> ... - asked by Simon (3 votes) ### 5.24 Tuesday, July 19, 2016 ================================== Top new questions this week: ================================== [How can I better mimic the graphics at earth.nullschool.net?] http://mathematica.stackexchange.com/questions/120842/how-can-i-better-mimic-the-graphics-at-earth-nullschool-net I’d like to be able to better mimic the graphics at earth.nullschool.net using Mathematica and I’m looking for suggestions for either improving my code or getting directed to some other approach. ... - asked by Jim Baldwin (14 votes), answered by Simon Woods (15 votes) —————————- [how to permute list of number1,2,3,...,n,while preserve the order of ﬁrst m terms as well as the last n-m terms?] http://mathematica.stackexchange.com/questions/120690/how-to-permute-list-of-number1-2-3-n-while-preserve-the-order-of-first-m-t For example, starting from 1,2,3,4, I want to generate all permutations like 1,3,2,4,1,3,4,2,3,4,1,2 which preserve the order of e.g ﬁrst two terms 1,2 and the order of e.g. last two terms ... - asked by user41614 (12 votes), answered by Kuba (8 votes) —————————- [Create a polynomial of a given degree] http://mathematica.stackexchange.com/questions/120841/create-a-polynomial-of-a-given-degree In Mathematica, how can I create a polynomial function in given variables of a given degree with unknown coeﬃcents? That is, I am looking for a function Poly[vars, degree] that generates, for ... - asked by Posch79 (11 votes), answered by march (6 votes) —————————- [Fractal basins of attraction in a Magnetic Pendulum] http://mathematica.stackexchange.com/questions/120946/fractal-basins-of-attraction-in-a-magnetic-pendulum I am trying to write a Mathematica program that realizes a graphical approximation of the basins of attraction in a Magnetic pendulum subject to friction and gravity, in which the three magnets are ... - asked by bharb (10 votes), answered by C. E. (9 votes) —————————- [Draw half empty rectangle] http://mathematica.stackexchange.com/questions/120781/draw-half-empty-rectangle How can I draw an half or a third ﬁlled rectangle? I want to make one rectangle frame with a unity width and then ﬁlled it according to a value between 0 and 1. - asked by Miguel (9 votes), answered by Feyre (9 votes) —————————- [How to access ”Choose Color Scheme” Programmatically] http://mathematica.stackexchange.com/questions/120999/how-to-access-choose-color-scheme-programmatically I am designing an App and I want to use the ”Choose Color Scheme” tools inside Button. I am looking to have this tool in popup window when the Button is clicked but I can’t ﬁnd the command to get ... - asked by Algohi (8 votes), answered by Karsten 7. (9 votes) —————————- [Programming the ﬁver game] http://mathematica.stackexchange.com/questions/120959/programming-the-fiver-game Obviously, even if I ask a lot of question I am, obviously, still a dummy!!!! I want to program the ﬁver game. It’s a very simple game played solitary on a $$5 \times 5$$ the rule is elementary : if ... - asked by cyrille.piatecki (8 votes), answered by Mr.Wizard (15 votes) ================================== Greatest hits from previous weeks: ================================== [Creating 3D dice] http://mathematica.stackexchange.com/questions/110295/creating-3d-dice How to create an image of a 3D die from the 2D images? There is an example in the Documentation Center I tried but it doesn’t work. - asked by vito (13 votes), answered by Martin Ender (21 votes) —————————- [xkcd-style graphs] http://mathematica.stackexchange.com/questions/11350/xkcd-style-graphs I received an email to which I wanted to respond with a xkcd-style graph, but I couldn’t manage it. Everything I drew looked perfect, and I don’t have enough command over PlotLegends to have these ... - asked by Amatya (518 votes), answered by Simon Woods (371 votes) ================================== Can you answer these? ================================== [How to increase the image resolution of a map?] http://mathematica.stackexchange.com/questions/120572/how-to-increase-the-image-resolution-of-a-map I’d like to obtain higher-resolution geographic maps retrieved from Wolfram geo server, since the standard resolution seems poor. I tried to increase the ”TileSize” parameter, like this: ... - asked by Fred (2 votes) —————————- [Hidden Markov Model: emissions probabilities dependent on observable parameter] http://mathematica.stackexchange.com/questions/120700/hidden-markov-model-emissions-probabilities-dependent-on-observable-parameter I need to ﬁt an HMM where the emission probabilities (ep) are discrete and dependent on a known variable quantity. E.g.: Imagine a daily time series of binary emissions (”1” or ”2”). I suppose an ... - asked by CupiDio (1 vote) —————————- [Why are there these jagged ”shards” in my RegionPlot3D?] http://mathematica.stackexchange.com/questions/120712/why-are-there-these-jagged-shards-in-my-regionplot3d I’m creating a region out of two component regions. Before anyone suggests it (because a lot of similar questions are about it), I don’t think the problem is increasing PlotPoints. I’ve increased it ... - asked by YungHummmma (1 vote) ### 5.25 Tuesday, July 12, 2016 ================================== Top new questions this week: ================================== [How to extract the list of all matrices from a Block Diagonal Matrix?] http://mathematica.stackexchange.com/questions/120433/how-to-extract-the-list-of-all-matrices-from-a-block-diagonal-matrix I am working on a function to do the opposite operation of How to form a block-diagonal Matrix from a list of matrices? Here is my current algorithm: For i starting at 1, scan the elements of index ... - asked by happy ﬁsh (11 votes), answered by yode (6 votes) —————————- [Collect all inputs from Documentation Center] http://mathematica.stackexchange.com/questions/120334/collect-all-inputs-from-documentation-center Is it possible to collect all inputs programmatically from every function in the Documentation Center in a list and wrap them in a HoldComplete? My case: With some fundamental functions modiﬁed, I ... - asked by happy ﬁsh (9 votes), answered by Edmund (12 votes) —————————- [How to avoid procedural loops in this example?] http://mathematica.stackexchange.com/questions/120533/how-to-avoid-procedural-loops-in-this-example I want to iterate over a list, and return the index as long as I found the ﬁrst element satisfying my condition. Written in a for loop: f[x_]:=2x For[i=1, i&lt;=10, i++, If[f[i]==10, Return[i]] ] ... - asked by Nick (8 votes), answered by Gerli (5 votes) —————————- [Why does this LibraryLink function crash?] http://mathematica.stackexchange.com/questions/120384/why-does-this-librarylink-function-crash Recently, I have rewritten pure Wolfram Language implementation CAGDBSplineSurface[] with C. Below is main LibraryLink code: LibraryLink Code #include "WolframLibrary.h" ... - asked by Shutao TANG (8 votes), answered by happy ﬁsh (11 votes) —————————- [How can I combine a list of Line[]’s into one continuous Line?] http://mathematica.stackexchange.com/questions/120285/how-can-i-combine-a-list-of-lines-into-one-continuous-line I have a huge list of Lines. Take this one as an example: linelist1 = {Line[{{0.15042300130733277, 0.09918669845167598}, {0.15124668865085406, 0.09522452324491057}}], ... - asked by YungHummmma (8 votes), answered by Michael E2 (12 votes) —————————- [NIntegrate appears to give incorrect results] http://mathematica.stackexchange.com/questions/120118/nintegrate-appears-to-give-incorrect-results I am trying to specify a bivariate probability density function in Mathematica. As a check, I would like to conﬁrm that it integrates to one. Here is the function: f[x1_, x2_, u1_, u2_, v11_, v22_, ...  - asked by Miguel (8 votes), answered by Anton Antonov (11 votes) —————————- [Which fonts are supported in Wolfram Cloud?] http://mathematica.stackexchange.com/questions/120102/which-fonts-are-supported-in-wolfram-cloud I recently suggested creating dynamic community ads with Wolfram Cloud. @C.E. made a proof of concept ad to show that it works well. Fonts are an important part of graphics design. It is useful to ... - asked by Szabolcs (8 votes), answered by Szabolcs (5 votes) ================================== Greatest hits from previous weeks: ================================== [What is the best Mathematica tutorial for young people?] http://mathematica.stackexchange.com/questions/733/what-is-the-best-mathematica-tutorial-for-young-people As Conrad Wolfram said at the TED conference, in the future kids should focus more on new technology. Computers compute better than humans, so we should focus more on thinking and getting the ... - asked by noisy (44 votes), answered by Vitaliy Kaurov (23 votes) —————————- [Mathematica Minecraft] http://mathematica.stackexchange.com/questions/19669/mathematica-minecraft Some time ago I asked myself: with all these great graphics and interactive capabilities of Mathematica, what kinds of 3D games can be implemented in it? And the answer which came to mind is ... - asked by faleichik (140 votes), answered by faleichik (192 votes) ================================== Can you answer these? ================================== [integrate giving wrong result] http://mathematica.stackexchange.com/questions/120495/integrate-giving-wrong-result A question with the same title has been asked many times, but I can’t ﬁnd the solution of my problem in their answers. The integral I am trying to calculate is Integrate[Sin[q ]^2 / Sinh[q]^2, {q, ... - asked by Felix (7 votes) —————————- [Why FinancialDerivative fails for the Spread case?] http://mathematica.stackexchange.com/questions/120277/why-financialderivative-fails-for-the-spread-case According to the documentation center for FinancialDerivative in version 10.4, when there are multi assets, we still may use FinancialDerivative with the corresponding correlation matrix to ﬁnd the ... - asked by M.J.2 (2 votes) —————————- [What does the GraphLayout -¿ ”SpectralEmbedding” option do (mean) when displaying a graph?] http://mathematica.stackexchange.com/questions/120139/what-does-the-graphlayout-spectralembedding-option-do-mean-when-displayin I have some relational data represented as a graph. As such some of the relational properties can be recognized. When I use the GraphLayout -¿ ”SpectralEmbedding” option a very nice and sharply ... - asked by Phillip Dukes (5 votes) ### 5.26 Tuesday, July 5, 2016 ================================== Top new questions this week: ================================== [Which Object-oriented paradigm approach to use in Mathematica?] http://mathematica.stackexchange.com/questions/119991/which-object-oriented-paradigm-approach-to-use-in-mathematica Which Object-Oriented Paradigm (OOP) approach to use in Mathematica for: general implementation, or a particular project? There are a lot of related questions and answers in MSE on doing OOP that ... - asked by Anton Antonov (14 votes) —————————- [How can I use Mathematica to sort the US Congressional Districts by Perimeter÷Area] http://mathematica.stackexchange.com/questions/119944/how-can-i-use-mathematica-to-sort-the-us-congressional-districts-by-perimeter%c3%b7ar The United States is divided into 435 congressional districts. Some of their shapes can be really strange due to gerrymandering. I think that I can ﬁnd very gerrymandered congressional districts if ... - asked by QuantumDot (13 votes), answered by Emilio Pisanty (6 votes) —————————- [Gillespie Stochastic Simulation Algorithm] http://mathematica.stackexchange.com/questions/119786/gillespie-stochastic-simulation-algorithm The Gillespie SSA is a Monte Carlo stochastic simulation algorithm to ﬁnd the trajectory a dynamic system described by a reaction (or interaction) network, e.g. chemical reactions or ecological ... - asked by István Zachar (13 votes), answered by István Zachar (15 votes) —————————- [How to create a fascinating QR code like this?] http://mathematica.stackexchange.com/questions/120041/how-to-create-a-fascinating-qr-code-like-this Check the facinating QRCode in my proﬁle page here You can ﬁnd that this QRCode is some sort of intriguing as the QRCode is a IMAGE ITSELF!!! So my question is, how to create such a QRCode ... - asked by Wjx (11 votes), answered by Wjx (11 votes) —————————- [Data extraction from a picture of a graph] http://mathematica.stackexchange.com/questions/119666/data-extraction-from-a-picture-of-a-graph How can I extract data from this picture of a graph? i = Import["http://i.stack.imgur.com/Ac8m0.png"]; The caption of the picture reads: ” Two-dimensional histogram values measured . Tick labels ... - asked by psimeson (10 votes), answered by Simon Woods (16 votes) —————————- [Evaluating summations involving Fibonacci numbers in terms of Fibonacci numbers] http://mathematica.stackexchange.com/questions/119822/evaluating-summations-involving-fibonacci-numbers-in-terms-of-fibonacci-numbers There are many summations involving Fibonacci numbers which Mathematica 10.4 is able to evaluate directly in terms of Fibonacci numbers. For example, Mathematica evaluates the summation given below as ... - asked by John M. Campbell (9 votes), answered by yarchik (4 votes) —————————- [TreeForm outputs diﬀerent results for the same inputs but why?] http://mathematica.stackexchange.com/questions/119745/treeform-outputs-different-results-for-the-same-inputs-but-why First of all, please look at the below inputs and outputs: In[1]:= a = Array[# Range[#] &amp;, {5}] Out[1]= {{1}, {2, 4}, {3, 6, 9}, {4, 8, 12, 16}, {5, 10, 15, 20, 25}} In[2]:= af = Flatten[a, ... - asked by Taiki Bessho (8 votes), answered by JasonB (11 votes) ================================== Greatest hits from previous weeks: ================================== [How to plot an ellipse?] http://mathematica.stackexchange.com/questions/20100/how-to-plot-an-ellipse I’m new to Mathematica, and I’m ﬁnding it diﬃcult to plot an ellipse. I tried using Plot[(x/5)^2 + (y/3)^2 == 1, {x, -5, 5}, {y, -3, 3}] but I’m getting some errors. Is there something wrong ... - asked by Sriram (6 votes), answered by Jens (15 votes) —————————- [Is it possible to draw this ﬁgure using Mathematica?] http://mathematica.stackexchange.com/questions/110848/is-it-possible-to-draw-this-figure-using-mathematica The ﬁgure is See the how-to video or a speeded-up GIF. I believe it should be possible to draw this ﬁgure programmatically using some Random function, but I’m rather new to Mathematica, so I ... - asked by AccidentalFourierTransform (50 votes), answered by M.R. (75 votes) ================================== Can you answer these? ================================== [Hide Notebook scrollbars] http://mathematica.stackexchange.com/questions/119665/hide-notebook-scrollbars Is it possible to hide the scrollbars from the notebook windows while still being able to use the mousewheel to scroll? Since I never click on the bars themselves they’re just a waste of space. It’s ... - asked by Ray (3 votes) —————————- [Hold Values of DensityPlot to use for an other DensityPlot] http://mathematica.stackexchange.com/questions/120022/hold-values-of-densityplot-to-use-for-an-other-densityplot I have two surface functions, f[x,y] and g[x,y]. Assuming that the DensityPlot of f and g takes a while, is there a way to hold the values of DensityPlot, to eﬃciently DensityPlot f[x,y]-g[x,y] ? ... - asked by Pierre L. (1 vote) —————————- [How to place window on second screen?] http://mathematica.stackexchange.com/questions/119835/how-to-place-window-on-second-screen I am trying to open a window on a second screen (a thunderbolt display attached to a macbook pro) that is the full size of the second screen. Here is the command I use: ThunderboltDimensions = 2560, ... - asked by abwatson (1 vote) ### 5.27 Tuesday, June 28, 2016 ================================== Top new questions this week: ================================== [Is the renaming mechanism of ‘With‘ ﬂawed?] http://mathematica.stackexchange.com/questions/119403/is-the-renaming-mechanism-of-with-flawed I’m confused about the renaming mechanism of With: With[{x = a}, Hold[With[{a = b}, a + 2 x]]] (*==&gt;Hold[With[{a = b}, a + 2 a]]*) With[{x = a}, Hold[With[{a = b}, a + 2 x]]] ...  - asked by luyuwuli (21 votes), answered by Leonid Shifrin (22 votes) —————————- [How do I increase the readability of this code?] http://mathematica.stackexchange.com/questions/119074/how-do-i-increase-the-readability-of-this-code Below is some code I am working on; being a beginner. How can I increase the readability of the part behind Manipulate? I can’t read my own code anymore, because it is simply too long and unordered. ... - asked by Imre Vegh (20 votes), answered by E.Doroskevic (16 votes) —————————- [Mysterious behaviour of Pick] http://mathematica.stackexchange.com/questions/119223/mysterious-behaviour-of-pick As everyone knows, Pick can do amazing things, The most facinating phenomenon is that it can pick though all sorts of lists: The basic &amp; pattern matching: Pick[{4, 5, 6}, {1, 2, 1}, 1] (*{4,6}*) ...  - asked by Wjx (18 votes), answered by WReach (25 votes) —————————- [How to debug the C code for LibraryLink?] http://mathematica.stackexchange.com/questions/119053/how-to-debug-the-c-code-for-librarylink Recently, I use the C to rewrite a Mathematica function NonzeroBasis[], please see here for fully descriptions. Here, NonzeroBasis[i,p,u,U] calculates the values of ... - asked by Shutao TANG (11 votes), answered by Szabolcs (16 votes) —————————- [Is it possible to attach a debugger to a dynamically linked library on the supported OS?] http://mathematica.stackexchange.com/questions/119083/is-it-possible-to-attach-a-debugger-to-a-dynamically-linked-library-on-the-suppo Recently, I discovered that LibraryLink technique is a very useful tool to improve the performance of function. Firstly, I need to use LibraryLink template to write C/C++ program. Then compiling the ... - asked by Shutao TANG (10 votes), answered by user21 (3 votes) —————————- [Nothing not behaving as expected?] http://mathematica.stackexchange.com/questions/119239/nothing-not-behaving-as-expected I was thinking that Nothing was doing the same job as the vanishing sequence ##&amp;[]. Yet this exemple shows it doesn't. Association[If[True,Nothing]] (*returns Association[Nothing]*) ... - asked by faysou (10 votes), answered by Szabolcs (12 votes) —————————- [Random walk on a Sierpinski gasket] http://mathematica.stackexchange.com/questions/119036/random-walk-on-a-sierpinski-gasket I am trying to simulate a random walk on a Sierpinski gasket. The best strategy i could come up with is to use Nearest point function to determine the next possible step of my walker. But this creates ... - asked by FEARxxx (9 votes), answered by Wjx (11 votes) ================================== Greatest hits from previous weeks: ================================== [Creating legends for plots with multiple lines?] http://mathematica.stackexchange.com/questions/4025/creating-legends-for-plots-with-multiple-lines So I have a graph with multiple lists, for e.g. data = {{1,2}, {3,4}, {3,5}, {2,3} . . .} If I then do ListLinePlot[Table[{#1,Log[b,#2]}&amp;@@@data, {b,1,10,2}]] I have no way to generate a legend ...  - asked by Eiyriou von Kauyf (58 votes), answered by Jens (88 votes) —————————- [How can this image (optical illusion) be created with Mathematica?] http://mathematica.stackexchange.com/questions/24148/how-can-this-image-optical-illusion-be-created-with-mathematica I came across this image the other day: and liked the sensation of it pulsing. I was wondering if anyone would know how to create something similar with Mathematica (without the Pink Floyd Dark ... - asked by Mike Honeychurch (51 votes), answered by halirutan (65 votes) ================================== Can you answer these? ================================== [Is pattern matching just systematic guessing and checking?] http://mathematica.stackexchange.com/questions/119394/is-pattern-matching-just-systematic-guessing-and-checking How does the pattern matcher work? how does it match this example? f[3, h[4]] /. f[x_, z_[y_]] :&gt; {x, y, z} My guess is that the pattern matcher collects all the names in the expression f[3, ... - asked by John Conor Cosnett (3 votes) —————————- [How can I move he documentation to another location after install on Windows?] http://mathematica.stackexchange.com/questions/119503/how-can-i-move-he-documentation-to-another-location-after-install-on-windows How can I move he documentation to another location after install on Windows? I would like to move the documentation to another partition on my Windows ﬁlesystem. Michael Hale in chat recommended ... - asked by jamesson (4 votes) —————————- [How to perform convolutions on this complicated pdf?] http://mathematica.stackexchange.com/questions/119034/how-to-perform-convolutions-on-this-complicated-pdf For a known pdf f[x], I need to calculate integrals over the probability density of the sum of Log[f[x]] over independent samples: Since the sample ... - asked by Jerry Guern (2 votes) ### 5.28 Tuesday, June 21, 2016 ================================== Top new questions this week: ================================== [$$3D$$ graphic of soccer ball] http://mathematica.stackexchange.com/questions/118604/3d-graphic-of-soccer-ball How to make a soccer ball $$3D$$ graphic? The following image is from Wikipedia, Spherical polyhedron: Truncated icosahedron (left) and standard soccer ball (right) ... - asked by vito (23 votes), answered by Michael E2 (23 votes) —————————- [The character sequence ” . d” triggers line break in strings] http://mathematica.stackexchange.com/questions/118801/the-character-sequence-d-triggers-line-break-in-strings Bug introduced in 7.0 or earlier and persists through 10.4.1 Bug isn’t present in version 5.2 Update: Sjoerd pointed out that this happens with any string and it is not related to StringForm. Just ... - asked by Szabolcs (14 votes), answered by Sjoerd C. de Vries (12 votes) —————————- [Inconsistent handling of Dynamic option values; intended, omission, or bug?] http://mathematica.stackexchange.com/questions/118646/inconsistent-handling-of-dynamic-option-values-intended-omission-or-bug In answering Dynamic ClipPlanes calculated from current ViewPoint Kuba and I got into a brief exchange regarding how Option values wrapped in Dynamic should be handled. For background John Fultz ... - asked by Mr.Wizard (14 votes) —————————- [How can I plot this spirally surface?] http://mathematica.stackexchange.com/questions/118887/how-can-i-plot-this-spirally-surface I would like to plot a surface that looks something like this sand spiral. But I really have no idea how. Ideally I would like to be able to express this as a function in cartesian coordinates. I’m ... - asked by user41147 (12 votes), answered by Thies Heidecke (28 votes) —————————- [Any manual on cell grouping management?] http://mathematica.stackexchange.com/questions/118649/any-manual-on-cell-grouping-management Recently I come back to the problem of cell grouping and performed extensive search on this site and on MathGroup archive for information on how to use the possible values of the CellGroupingRules ... - asked by Alexey Popkov (12 votes) —————————- [How can Mathematica be used to create Images like these?] http://mathematica.stackexchange.com/questions/118992/how-can-mathematica-be-used-to-create-images-like-these Here are two examples of artistic image interpolation using just black lines. The ﬁrst link shows the desired result created by an artist and the second done with C#. TRIANGULATION: ANGULAR ... - asked by R Hall (11 votes), answered by MarcoB (10 votes) —————————- [How to implement custom NIntegrate integration strategies?] http://mathematica.stackexchange.com/questions/118920/how-to-implement-custom-nintegrate-integration-strategies How can new integration strategies algorithms be used with NIntegrate? This is a diﬀerent type of extension than the extensions with new integration rules, as described in the answer for the ... - asked by Anton Antonov (10 votes), answered by Anton Antonov (10 votes) ================================== Greatest hits from previous weeks: ================================== [Fit image of mountain to gaussian] http://mathematica.stackexchange.com/questions/109946/fit-image-of-mountain-to-gaussian I want to detect the edges of an image of a mountain and then ﬁt that to a gaussian. I am unsure about how to only get the mountain edge, rather than every single edge in the image. How do I ... - asked by olliepower (13 votes), answered by Dr. belisarius (14 votes) —————————- [How to ﬁnd the position of elements in a list satisfying criteria] http://mathematica.stackexchange.com/questions/180/how-to-find-the-position-of-elements-in-a-list-satisfying-criteria Say I have a list x={2,4,6,8,10} and I want to find out the positions of the elements that are greater than 7. Select[x, #&gt;7&amp;] gives the elements themselves, and Position[x,8] gives the ...  - asked by PeterR (32 votes), answered by J. M. (29 votes) ================================== Can you answer these? ================================== [Softmax Regression Classiﬁcation Algorithm] http://mathematica.stackexchange.com/questions/118958/softmax-regression-classification-algorithm I’m following the Stanford Machine Learning course while simultaneously developing my Mathematica abilities. I’m having issues with my Softmax Classiﬁer implementation (for ref, have a look at these ... - asked by Frederik Brinck Jensen (4 votes) —————————- [Protected Variable Error with Workbench 3.0] http://mathematica.stackexchange.com/questions/118919/protected-variable-error-with-workbench-3-0 I have Wolfram Workbench 3.0, build 78, with Mathematica 10.4 as the front end. I am using Windows 10. I am trying to run a simple test source code test.m: fun[x_] := x^2; I have an empty notebook ... - asked by S2167 (2 votes) —————————- [Putting the elements of a list inside another list] http://mathematica.stackexchange.com/questions/118837/putting-the-elements-of-a-list-inside-another-list I have the list list1 = 1, 3, 4, 5, 6 and want to put the elements of this list inside a list of 0’s, list2 = 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, where each element of list1 will be in the ... - asked by user41129 (1 vote) ### 5.29 Tuesday, June 14, 2016 ================================== Top new questions this week: ================================== [Are you interested in a Wolfram Workbench Update?] http://mathematica.stackexchange.com/questions/118154/are-you-interested-in-a-wolfram-workbench-update I also posted this on the Wolfram Community site (link below) Last week I attended the Wolfram Tour (which was great). I asked whenever we could expect a new version of Workbench, as the current ... - asked by Frank Martin (18 votes), answered by Anton Antonov (14 votes) —————————- [Is manual adjustment of AccuracyGoal and PrecisionGoal useless?] http://mathematica.stackexchange.com/questions/118249/is-manual-adjustment-of-accuracygoal-and-precisiongoal-useless This is a problem confusing me for years. AccuracyGoal and PrecisionGoal are two options that I never truly understand and, to be honest, always avoid touching. Let’s ﬁrst look at the descriptions ... - asked by xzczd (15 votes) —————————- [Can Mathematica recompose an image?] http://mathematica.stackexchange.com/questions/117892/can-mathematica-recompose-an-image The OP in this post on superuser.com asks how to recompose an image; quoting: I have a set of images, which are parts of a bigger image. I would like the images to assembled as automated as ... - asked by mattiav27 (15 votes), answered by C. E. (13 votes) —————————- [How to implement custom integration rules for use by NIntegrate] http://mathematica.stackexchange.com/questions/118324/how-to-implement-custom-integration-rules-for-use-by-nintegrate How can NIntegrate be extended with custom implementation of integration rules? This answer of the question ”Monte Carlo integration with random numbers generated from a Gaussian distribution” shows ... - asked by Anton Antonov (14 votes), answered by Anton Antonov (15 votes) —————————- [Unexpected behavior of Sequence – using Sequence to delete parts of an expression] http://mathematica.stackexchange.com/questions/118108/unexpected-behavior-of-sequence-using-sequence-to-delete-parts-of-an-expressi I thought that assigning Sequence[] to the part of an expression was an eﬀective way to remove it. For example, the following code yields 2,3,4,5: xx = Range[5]; xx[[1]] = Sequence[]; xx Thus, I ... - asked by Hector (10 votes), answered by Leonid Shifrin (6 votes) —————————- [Why NIntegrate is badly-behaved on $$J_{\frac {9}{2}}(x)$$ by default?] http://mathematica.stackexchange.com/questions/117888/why-nintegrate-is-badly-behaved-on-j-frac92x-by-default A friend of mine showed me this example: Plot[BesselJ[9/2, x], {x, 0, 1}, PlotLabel -&gt; Style["The integrand seems to be simple", 14]] Integrate[BesselJ[9/2, x], {x, 0, 1}] // N (* ...  - asked by xzczd (10 votes), answered by Anton Antonov (6 votes) —————————- [How do I insert OwnValues inside a held expression without evaluating it?] http://mathematica.stackexchange.com/questions/118030/how-do-i-insert-ownvalues-inside-a-held-expression-without-evaluating-it Here is a very long and complicated expression, which we abbreviate as a. I store it using SetDelayed because I want to perform algebraic manipulations on it: ClearAll[a]; a := 1 + 1 Here is a ... - asked by QuantumDot (9 votes), answered by Kuba (9 votes) ================================== Greatest hits from previous weeks: ================================== [Where can I ﬁnd examples of good Mathematica programming practice?] http://mathematica.stackexchange.com/questions/18/where-can-i-find-examples-of-good-mathematica-programming-practice I consider myself a pretty good Mathematica programmer, but I’m always looking out for ways to either improve my way of doing things in Mathematica, or to see if there’s something nifty that I haven’t ... - asked by J. M. (419 votes), answered by faysou (377 votes) —————————- [++ is dangerous for C programmers] http://mathematica.stackexchange.com/questions/107619/is-dangerous-for-c-programmers I noticed this fact, that may be misleading for programmers used to C language. In Mathematica, if you have a function f[] and an array v, and you write v[[ f[] ]]++ the function f is called ... - asked by Giovanni Resta (32 votes), answered by Mr.Wizard (24 votes) ================================== Can you answer these? ================================== [Solve and design ”water ﬂow”] http://mathematica.stackexchange.com/questions/118183/solve-and-design-water-flow In some strategy game I play, I’ll have to change the terrain to make the water ﬂow in some speciﬁc way to fulﬁll my goal. The water ﬂow changes with terrain so if I can change the terrain wisely ... - asked by Wjx (5 votes) —————————- [Is there a way to ﬁgure out the ”upper limit” of my PC’s computational ability in Mathematica?] http://mathematica.stackexchange.com/questions/117852/is-there-a-way-to-figure-out-the-upper-limit-of-my-pcs-computational-ability I am doing some simulations with Finite Element Analysis (FEA) and part of it is forming a mesh in 3D and then using NDSolveValue to solve a diﬀerential equation on that mesh. For some meshes, my ... - asked by YungHummmma (2 votes) —————————- [Numerical testing of Hardy’s inequality] http://mathematica.stackexchange.com/questions/118061/numerical-testing-of-hardys-inequality I want to check the following Hardy’s most fundamental inequality by using Mathematica: ... - asked by vito (2 votes) ### 5.30 Tuesday, June 7, 2016 ================================== Top new questions this week: ================================== [Bug with MapAt, Span, and Association?] http://mathematica.stackexchange.com/questions/116561/bug-with-mapat-span-and-association Bug introduced in 10.0 and persisting through 10.4.1 or later Related to Mapping (Query) a function at multiple locations in nested data via All, Span, it seems to me that the behavior of MapAt ... - asked by Mr.Wizard (19 votes) —————————- [Joining points into 3D surface] http://mathematica.stackexchange.com/questions/117736/joining-points-into-3d-surface This seems like a simple problem, but I can’t ﬁnd any questions like it here so I’m making a new one. Apologies if I missed one. I have a list of points contained in a ﬁle which can be visualized ... - asked by Crepo (12 votes), answered by george2079 (6 votes) —————————- [How to check the validity of an option value] http://mathematica.stackexchange.com/questions/116623/how-to-check-the-validity-of-an-option-value I have a user-deﬁned function, func, which takes the following form:  func[arg1, arg2, options] Here is the actual code Options[func] = {opt1 -&gt; Automatic, opt2 -&gt; False, opt3 -&gt; {1, ... - asked by Shutao TANG (12 votes), answered by Leonid Shifrin (10 votes) —————————- [Why does the GeoGraphics Frame show diﬀerent Latitude than GeoPosition?] http://mathematica.stackexchange.com/questions/116507/why-does-the-geographics-frame-show-different-latitude-than-geoposition The map looks right, but the Latitude in the Frame looks wrong. Am I making a mistake or is this a bug? - asked by vonkohorn (12 votes), answered by jose (8 votes) —————————- [Rotate Geographic map] http://mathematica.stackexchange.com/questions/117744/rotate-geographic-map I want the map to be rotated by -45 Degree. I want to coast to be horizontal (perfect -45 degree). I already have: loc = GeoPosition[{52.57243, 5.51780}]; loc1 = GeoPosition[{52.57718, 5.52193}]; ... - asked by Dennis (11 votes) —————————- [How to learn the LibraryLink technique for the newcomer?] http://mathematica.stackexchange.com/questions/116451/how-to-learn-the-librarylink-technique-for-the-newcomer Description For the built-in programming language(or called Wolfram Language) of Wolfram Mathematica, I think it is much easier and simpler to learn than other computer language(such as C/C++ or ... - asked by Shutao TANG (11 votes), answered by Szabolcs (12 votes) —————————- [Nested association values validation. POJsO handling] http://mathematica.stackexchange.com/questions/116571/nested-association-values-validation-pojso-handling Sometimes it is convenient to work in your package/app with ”objects” like: childObject = &lt;| "id" -&gt; 284, "text" -&gt; "texttext", "property" -&gt; &lt;| "type" -&gt; "String", ... - asked by Kuba (9 votes), answered by Leonid Shifrin (5 votes) ================================== Greatest hits from previous weeks: ================================== [Where can I ﬁnd examples of good Mathematica programming practice?] http://mathematica.stackexchange.com/questions/18/where-can-i-find-examples-of-good-mathematica-programming-practice I consider myself a pretty good Mathematica programmer, but I’m always looking out for ways to either improve my way of doing things in Mathematica, or to see if there’s something nifty that I haven’t ... - asked by J. M. (417 votes), answered by faysou (376 votes) —————————- [How to create word clouds?] http://mathematica.stackexchange.com/questions/2334/how-to-create-word-clouds Word clouds are rather useless fancy and visually appealing plots, where words are plotted with diﬀerent sizes according to their frequency in a corpus. Many applications exist out there (Wordle, ... - asked by Istvan Zachar (126 votes), answered by Heike (105 votes) ================================== Can you answer these? ================================== [What is the diﬀerence between getting a boundary mesh from ToBoundaryMesh vs doing it with ToElementMesh?] http://mathematica.stackexchange.com/questions/116559/what-is-the-difference-between-getting-a-boundary-mesh-from-toboundarymesh-vs-do I am trying to ﬁgure out how to deﬁne and use meshes for FEM and NDSolve. I’ve ﬁgured out that if I want more resolution near my boundaries, I can use ToBoundaryMesh to ﬁrst create the boundary ... - asked by YungHummmma (4 votes) —————————- [Solving Diﬀerential Equation for derivative] http://mathematica.stackexchange.com/questions/117689/solving-differential-equation-for-derivative I am new to mathematica and am trying to solve a diﬀerential equation. Actually, I am not entirely sure if the system can be called diﬀerential equation. I am interested in ﬁnding out the second ... - asked by JKJ (1 vote) —————————- [ShortestTour Problem with Constraints] http://mathematica.stackexchange.com/questions/116505/shortesttour-problem-with-constraints I can solve a travelling salesman problem with FindShortestTour[], but couldn’t ﬁnd any function to solve a shorest tour problem with additional constraints like cost, fuel capacity etc. How cam I ... - asked by user40405 (3 votes) ### 5.31 Tuesday, May 31, 2016 ================================== Top new questions this week: ================================== [Determine whether points lie within a cow] http://mathematica.stackexchange.com/questions/116160/determine-whether-points-lie-within-a-cow I would like to determine whether randomly-generated points lX = RandomVariate[UniformDistribution[{-0.4, 0.4}], {1000}]; lY = RandomVariate[UniformDistribution[{-0.2, 0.2}], {1000}]; lZ = ...  - asked by ben18785 (18 votes), answered by Daniel Lichtblau (12 votes) —————————- [FindMinimum doesn’t increase step size when necessary] http://mathematica.stackexchange.com/questions/116295/findminimum-doesnt-increase-step-size-when-necessary I’ve spent much time ﬁnding a minimal example demonstrating this problem with FindMinimum. Normally one faces this problem when ﬁtting very large and complicated functions which cannot be posted ... - asked by Alexey Popkov (13 votes) —————————- [Internal DynamicModule steals scope of external DynamicModule] http://mathematica.stackexchange.com/questions/116167/internal-dynamicmodule-steals-scope-of-external-dynamicmodule I have two dynamic objects, one nested in the other. Both have their own functions deﬁned, as follows. I have simpliﬁed them to the point where they don’t make much sense, but can still illustrate ... - asked by Istvan Zachar (13 votes), answered by John Fultz (6 votes) —————————- [Opposite of Alternatives in a Rule] http://mathematica.stackexchange.com/questions/116302/opposite-of-alternatives-in-a-rule Mathematica provides Alternatives, to match one of several patterns. In a rule, this is used as p1|p2|p3:&gt;replacement. I would like to have the opposite logic: p1&amp;p2&amp;p3:&gt;replacement ... - asked by Bruno Le Floch (10 votes), answered by Bruno Le Floch (8 votes) —————————- [Symbolic and numeric limit disagreeing on branch cut of ArcTan] http://mathematica.stackexchange.com/questions/116183/symbolic-and-numeric-limit-disagreeing-on-branch-cut-of-arctan Bug introduced after v8.0.4 and before v9.0.1, and persisting through v10.4.1. Investigating comments to my previous question lead me to the following problem:  N[Limit[ ArcTan[Sqrt[-4 E^(I a)]], ... - asked by Axel Boldt (9 votes), answered by bbgodfrey (9 votes) —————————- [Why does the global variable exist here, where it was declared only in Module?] http://mathematica.stackexchange.com/questions/116140/why-does-the-global-variable-exist-here-where-it-was-declared-only-in-module Why does Mathematica choose the mechanism that makes the global variable a here while parsing? In f := Module[{a}, a;] In ?a Out Globala I don’t understand why Mathematica goes in the way ... - asked by Smart Humanism (8 votes), answered by Leonid Shifrin (15 votes) —————————- [Integrate and NIntegrate disagreeing over branch cut of Sqrt?] http://mathematica.stackexchange.com/questions/116041/integrate-and-nintegrate-disagreeing-over-branch-cut-of-sqrt Bug introduced after v8.0.4 and before v9.0.1, and persisting through v10.4.1. In Mathematica 10.2 I’m trying to integrate this piecewise continuous function, but Integrate and NIntegrate seem to ... - asked by Axel Boldt (8 votes), answered by bbgodfrey (6 votes) ================================== Greatest hits from previous weeks: ================================== [Generating a Sierpinski carpet] http://mathematica.stackexchange.com/questions/22052/generating-a-sierpinski-carpet I am trying to draw a Sierpinski_carpet. I have code that works, but I think there is a more elegant way to do than my way. Maybe I couls use Tuples or Permutations or some similar function to ... - asked by chyaong (43 votes), answered by Mr.Wizard (67 votes) —————————- [Drawing a square root spiral] http://mathematica.stackexchange.com/questions/66969/drawing-a-square-root-spiral Here is a start. I’m looking for a nice way to draw it. Graphics[{EdgeForm[Black], White, Polygon @ {{0, 0}, {-1, 0}, Sqrt[2] {Cos[#], Sin[#]} &amp;[Pi - (ArcCot[1])]}, Polygon @ {{0, ... - asked by mathe (22 votes), answered by Bob Hanlon (18 votes) ================================== Can you answer these? ================================== [Problem with Parallelization when using Packages] http://mathematica.stackexchange.com/questions/115862/problem-with-parallelization-when-using-packages I tried to ﬁnd a solution to my problem in several answers posted in MSE but due to lack of my knowledge on parallelization territory, I couldn’t ﬁgure out solution to my problem. I have a big code ... - asked by Algohi (4 votes) —————————- [Fourier transform of Exp[x]/x] http://mathematica.stackexchange.com/questions/116157/fourier-transform-of-expx-x Could you please explain why Mathematica gives the following expression when taking Fourier transform of $$\exp (\lambda z)/\lambda$$? Why the answer does not ... - asked by Ivan Gankevich (4 votes) —————————- [Inconsistent behavior from RegionMeasure on the RegionIntersection between a Polygon and a Line] http://mathematica.stackexchange.com/questions/116083/inconsistent-behavior-from-regionmeasure-on-the-regionintersection-between-a-pol Consider a Polygon with lines drawn between two of its vertices, pgon = Get[ "https://gist.githubusercontent.com/jasondbiggs/\ 59cb7d4aa802bde68c9f6a5203ef698f/raw/\ ... - asked by Jason is no longer a postdoc (1 vote) ### 5.32 Tuesday, May 24, 2016 ================================== Top new questions this week: ================================== [Pulsed NMR animation] http://mathematica.stackexchange.com/questions/115675/pulsed-nmr-animation I’m new here and have never interacted with the community so excuse me if this has been asked before or if I format incorrectly or anything like that. Anyway, I’m trying to make an animation for a ... - asked by D. Sessions (13 votes), answered by Jack LaVigne (16 votes) —————————- [Plot 3D model of DNA in Mathematica] http://mathematica.stackexchange.com/questions/115491/plot-3d-model-of-dna-in-mathematica My friend asked me if we can plot a 3D model of DNA (deoxyribonucleic acid) in Mathematica. However, I am not really familiar with this and I don’t know if Mathematica can do this. Could you answer ... - asked by BlueSky (12 votes), answered by JasonB (23 votes) —————————- [Exclude overlapping lists while keeping disjoint- and sub-lists?] http://mathematica.stackexchange.com/questions/115545/exclude-overlapping-lists-while-keeping-disjoint-and-sub-lists Consider a function f[l1_List,l2_List] which is given lists of integers. Whenever two of the lists contain completely disjoint sets of integers OR one of the lists is completely contained in the ... - asked by Kagaratsch (12 votes), answered by ciao (15 votes) —————————- [Beautiful dance of the Earth and Venus around the sun] http://mathematica.stackexchange.com/questions/115358/beautiful-dance-of-the-earth-and-venus-around-the-sun I have seen very nice dynamic graphics created by users of Ma. I would like to get help whether the following graphics can be created using Ma. I was not able to create the dynamic picture here. ... - asked by ramesh (11 votes), answered by ubpdqn (6 votes) —————————- [Second argument of BeginPackage with nested package loading] http://mathematica.stackexchange.com/questions/115502/second-argument-of-beginpackage-with-nested-package-loading I naively thought that the second argument of BeginPackage can simply be used to ensure the loading and availability in the ContextPath of additional packages. Example: (* Pack1.m *) ... - asked by Szabolcs (11 votes), answered by Leonid Shifrin (7 votes) —————————- [How to correctly implement in a new function the scoping behavior of Table, Sum and other commands that use Block to localize iterators?] http://mathematica.stackexchange.com/questions/115722/how-to-correctly-implement-in-a-new-function-the-scoping-behavior-of-table-sum It is documented that ”Block is automatically used to localize values of iterators in iteration constructs such as Do, Sum, and Table.” Therefore the dummy index (iterator) in a Sum is shielded ... - asked by MaTECmatica (9 votes), answered by Leonid Shifrin (6 votes) —————————- [Parallelization works, but does not use all CPU power] http://mathematica.stackexchange.com/questions/115436/parallelization-works-but-does-not-use-all-cpu-power I’ve written code which involves Parallelize@Cases. When I evaluate, I ﬁnd that all 16 cores are being used, but not fully; in other words all cores are active, but the total CPU usage is only 50 ... - asked by Luther (8 votes), answered by Szabolcs (17 votes) ================================== Greatest hits from previous weeks: ================================== [How was Mathematica built?] http://mathematica.stackexchange.com/questions/106020/how-was-mathematica-built I’ve been wondering this for a while now: How was Mathematica built? Is it written in Haskell? C++? I’d love to get a taste of the wizardry behind this incredible software. - asked by Chet (17 votes), answered by Sjoerd C. de Vries (23 votes) —————————- [How do I clear all user deﬁned symbols?] http://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 (42 votes), answered by Artes (36 votes) ================================== Can you answer these? ================================== [How can I deﬁne MakeBoxes for Inactive forms user-deﬁned heads?] http://mathematica.stackexchange.com/questions/115638/how-can-i-define-makeboxes-for-inactive-forms-user-defined-heads Here I deﬁne a MakeBoxes for Times: MakeBoxes[p : Inactive[Times][args___], form_] := MakeBoxes[Interpretation[HoldForm@myHead[args], p], form] And it works as expected: Inactivate[Times[3, ... - asked by QuantumDot (2 votes) —————————- [Quits Kernel during evaluation of CreateTopologies] http://mathematica.stackexchange.com/questions/115660/quits-kernel-during-evaluation-of-createtopologies I am using Feynarts 3.9 and FeynCalc 9.0.1 with Mathematica 10. Every time I load FeynArts with FeynCalc and execute t = CreateTopologies[1, 1 -&gt; 2]; mathematica quits the kernel after a few ... - asked by Heerak Banerjee (1 vote) —————————- [Inconsistent performance of code] http://mathematica.stackexchange.com/questions/115634/inconsistent-performance-of-code I’m trying to do some optimizations to my code to make it run faster, but it seems that there are inconsistencies in the performance of the code. Namely, the codes have diﬀerent performance in ... - asked by xslittlegrass (5 votes) ### 5.33 Tuesday, May 17, 2016 ================================== Top new questions this week: ================================== [Speedup matrix number multiplication] http://mathematica.stackexchange.com/questions/115087/speedup-matrix-number-multiplication Consider this simple matrix number multiplication: lth = 200; mtx = RandomReal[{0, 1}, {lth, lth}]; ls = RandomReal[{0, 1}, {lth}]; Et = Function[{t}, Sin[(Pi t)/20] Sin[2 t]]; Etc = Compile[{{t, ... - asked by xslittlegrass (15 votes), answered by xslittlegrass (5 votes) —————————- [Fit a function with an unusual side condition] http://mathematica.stackexchange.com/questions/114864/fit-a-function-with-an-unusual-side-condition I have a set of measurement data and I try to ﬁt there a function (a Exp[b x] + c Exp[d x] - o). I have two problems: The ﬁt function does not converge nor after $$500$$ iterations. The ﬁt function ... - asked by Lutscher (12 votes), answered by Anton Antonov (15 votes) —————————- [Tips to move from functional programming to GUI-based applications] http://mathematica.stackexchange.com/questions/114984/tips-to-move-from-functional-programming-to-gui-based-applications Even though this forum has some questions related to Mathematica programming tips I think that we still don’t have speciﬁc help for those who want to learn to eﬃciently create GUIs in Mathematica. ... - asked by Ariel Sepulveda (11 votes), answered by Brian G (0 votes) —————————- [Longest common substring for multiple strings?] http://mathematica.stackexchange.com/questions/114979/longest-common-substring-for-multiple-strings I’m looking for a way to get the longest common substring for multiple strings such as  {home/dir1/dir2/jmoasd.txt,home/dir1/dir2/ivbnoxcihv.txt,home/dir1/dir2/siuhgiuchv.txt} should yield ... - asked by nqduy (10 votes), answered by xslittlegrass (9 votes) —————————- [How does a Pringle lose its curvature?] http://mathematica.stackexchange.com/questions/115231/how-does-a-pringle-lose-its-curvature Nom! As part of a bigger project, I’ve was writing some code to calculate the scalar curvature of surfaces of the form $$z = f(x,y)$$. This uses a general calculation of the scalar curvature to produce ... - asked by Lucas (9 votes), answered by KraZug (9 votes) —————————- [How to make datasets display correctly?] http://mathematica.stackexchange.com/questions/115246/how-to-make-datasets-display-correctly NB: The problem illustrated below is truly ubiquitous. I hope the examples given below are suﬃciently diﬀerent to demonstrate this fact, and to discourage answers that hinge on the details of the ... - asked by kjo (9 votes), answered by Stefan R (9 votes) —————————- [How do I translate a list of English words into another language using an online translation service with Mathematica?] http://mathematica.stackexchange.com/questions/115141/how-do-i-translate-a-list-of-english-words-into-another-language-using-an-online As far as I know, there are two posts on this topic: Can I use Mathematica to translate a English word to a Chinese characters? and *How can I use Mathematica to get the translated result from the ... - asked by matheorem (9 votes), answered by Rashid (11 votes) ================================== Greatest hits from previous weeks: ================================== [What is the best Mathematica tutorial for young people?] http://mathematica.stackexchange.com/questions/733/what-is-the-best-mathematica-tutorial-for-young-people As Conrad Wolfram said at the TED conference, in the future kids should focus more on new technology. Computers compute better than humans, so we should focus more on thinking and getting the ... - asked by noisy (43 votes), answered by Vitaliy Kaurov (23 votes) —————————- [How to make use of Associations?] http://mathematica.stackexchange.com/questions/52393/how-to-make-use-of-associations I have been curious about it for long. Now that Mathematica 10 arrives, I think it’s time to ask the question: How the new Association data structure would be used to improve Mathematica programming? ... - asked by Yi Wang (110 votes), answered by Leonid Shifrin (128 votes) ================================== Can you answer these? ================================== [PearsonChiSquareTest for count/frequency data?] http://mathematica.stackexchange.com/questions/114905/pearsonchisquaretest-for-count-frequency-data I read with interest a previous question on the PearsonChiSquareTest from a few years ago, and one answer was very helpful: Performing a chi-square goodness of ﬁt test Have there been any updates ... - asked by Jim (3 votes) —————————- [ParallelDo issue with SQLExecute (SQLite)] http://mathematica.stackexchange.com/questions/115263/paralleldo-issue-with-sqlexecute-sqlite This code run as expected if I use Do[...], but if I use instead ParallelDo[...], as in the code bellow, the SQL INSERT statements seems to be completely ignored. In both cases, the ﬁlename is ... - asked by jss (2 votes) —————————- [Why does Kernels[] produce this error?] http://mathematica.stackexchange.com/questions/115100/why-does-kernels-produce-this-error Most of times, on my PC, when Kernel[] is launched for the ﬁrst time, produces this error: Executed again returns . Is it a clue of malfunctioning or is, for reason I’m unaware of, the way it ... - asked by mitochondrial (3 votes) ### 5.34 Tuesday, May 10, 2016 ================================== Top new questions this week: ================================== [Understanding evaluation and typesetting] http://mathematica.stackexchange.com/questions/114305/understanding-evaluation-and-typesetting Background So, one could be surprised by the fact that: Hold @ Grid[{{1, 2}}] (*or*) Hold @ Graphics @ Disk[] This issue and methods of prevention are discussed in Prevent graphics render ... - asked by Kuba (16 votes), answered by Alexey Popkov (7 votes) —————————- [Empty WhenEvent action crashes kernel] http://mathematica.stackexchange.com/questions/114314/empty-whenevent-action-crashes-kernel Bug introduced in 9.0 and persisting through 10.4.1 WhenEvent is new in 9.0. This is an example from the docs, slightly modiﬁed (action is wrapped in ), working as expected. NDSolve[x’[t] == ... - asked by Istvan Zachar (12 votes), answered by Istvan Zachar (3 votes) —————————- [Diﬀerence between = and Ctrl + =] http://mathematica.stackexchange.com/questions/114357/difference-between-and-ctrl What is a diﬀerence between $$\textbf {=}$$, and Ctrl + $$\textbf {=}$$? For instance there are some examples, but result is same. and - asked by vito (11 votes), answered by WReach (19 votes) —————————- [Is there a way to make links to functions in a notebook?] http://mathematica.stackexchange.com/questions/114342/is-there-a-way-to-make-links-to-functions-in-a-notebook Frequently I’m working on a function that’s at the top of my notebook in a ”functions” section, but I’m looking at the output of it in a lower ”body” section of the notebook. When I want to edit the ... - asked by YungHummmma (11 votes), answered by Mr.Wizard (11 votes) —————————- [Strategies to compensate for lack of multi-document interface?] http://mathematica.stackexchange.com/questions/114515/strategies-to-compensate-for-lack-of-multi-document-interface I use Mathematica (Home Edition) to manage notes which live in a large number of diﬀerent notebooks. In my case the notebooks (hundreds) are just organized using document names and ﬁle system ... - asked by billc (10 votes), answered by Leonid Shifrin (10 votes) —————————- [Deﬁnition of Mod and Quotient with complex arguments] http://mathematica.stackexchange.com/questions/114361/definition-of-mod-and-quotient-with-complex-arguments How are Mod and Quotient deﬁned for three real/complex arguments? I wasn’t able to ﬁnd the deﬁnition. My main surprise so far when investigating their behavior is a discontinuity between real and ... - asked by Bruno Le Floch (10 votes), answered by Chip Hurst (10 votes) —————————- [HighlightGraph Problem] http://mathematica.stackexchange.com/questions/114725/highlightgraph-problem Bug introduced in 9.0 or earlier and persisting through 10.4.1 HighlightGraph does not work. HighlightGraph[Graph[{{0, 0}, {0, 1}, {1, 0}, {1, 1}}, {{0, 0} \[UndirectedEdge] {0, 1}}], {{0, 0}, {0, ... - asked by ZYX (8 votes), answered by Szabolcs (5 votes) ================================== Greatest hits from previous weeks: ================================== [Labeling individual curves in Mathematica] http://mathematica.stackexchange.com/questions/4444/labeling-individual-curves-in-mathematica I need to create a plot for export and inclusion in a report. Is there a better way to label curves than PlotLegends? From what I’ve read and my personal experience, PlotLegends is pretty bad. Is ... - asked by Tianxiang Xiong (42 votes), answered by Artes (36 votes) —————————- [Drawing a square root spiral] http://mathematica.stackexchange.com/questions/66969/drawing-a-square-root-spiral Here is a start. I’m looking for a nice way to draw it. Graphics[{EdgeForm[Black], White, Polygon @ {{0, 0}, {-1, 0}, Sqrt[2] {Cos[#], Sin[#]} &amp;[Pi - (ArcCot[1])]}, Polygon @ {{0, ... - asked by mathe (22 votes), answered by Bob Hanlon (17 votes) ================================== Can you answer these? ================================== [FrobeniusSolve: how does it work?] http://mathematica.stackexchange.com/questions/114308/frobeniussolve-how-does-it-work Can someone suggest any reference to read? I would like to understand how the algorithm works. - asked by Mirko Aveta (3 votes) —————————- [How to delete lines containing speciﬁc values from a matrix?] http://mathematica.stackexchange.com/questions/114709/how-to-delete-lines-containing-specific-values-from-a-matrix I am doing some numerical computations and a few iterations return values that are obviously incorrect (some numerical integration problem, I suppose.). I have managed to set these values to zero but ... - asked by Gabu (2 votes) —————————- [ImageSize not working correctly with Placed directive] http://mathematica.stackexchange.com/questions/114580/imagesize-not-working-correctly-with-placed-directive It seems that having Placed inside Plot breaks the ImageSize speciﬁcation: cm = 72/2.54; plt = LogLogPlot[Exp[x], {x, 1, 3}, ImageSize -&gt; 12 cm, AspectRatio -&gt; 0.73, Frame -&gt; ... - asked by leosenko (2 votes) ### 5.35 Tuesday, May 3, 2016 ================================== Top new questions this week: ================================== [Find duplicates in list of InﬁniteLine] http://mathematica.stackexchange.com/questions/114046/find-duplicates-in-list-of-infiniteline MMA 10 introduced a new function, which can be very convenient: InﬁniteLine. Of course, two inﬁnite lines can be described by diﬀerent arguments: for example InﬁniteLine[0,0,1,0] and ... - asked by anderstood (14 votes), answered by kglr (12 votes) —————————- [Is there any harm or beneﬁt to Removing unneeded private symbols in packages?] http://mathematica.stackexchange.com/questions/114106/is-there-any-harm-or-benefit-to-removing-unneeded-private-symbols-in-packages One of the things I noticed is that in typical medium-to-large sized packages, a huge number of symbols are created in the myPackage‘Private context. You can see a list of them by running ? ... - asked by QuantumDot (12 votes), answered by R. M. (18 votes) —————————- [Can Mathematica solve functional equations with nested variable?] http://mathematica.stackexchange.com/questions/114210/can-mathematica-solve-functional-equations-with-nested-variable First, inline free form input can solve these equations: But it seems no native Mathematica function can solve these, there is even an error page for equations of this form (nestdv). Now my ... - asked by happy ﬁsh (10 votes) —————————- [How to describe the convex hull of a set of points as an implicit region for optimization?] http://mathematica.stackexchange.com/questions/113689/how-to-describe-the-convex-hull-of-a-set-of-points-as-an-implicit-region-for-opt Last edit: 2016-05-03 A.G.’s answer was the one helped me the most, see explanation at the end of this question. Original question In Mathematica you can create out of a set of points in 2D and 3D ... - asked by Mauricio Lobos (10 votes), answered by A.G. (2 votes) —————————- [NDEigensystem returns incorrect eigenvalues for 2D coulomb problem, eigenfunctions contain discontinuity] http://mathematica.stackexchange.com/questions/113898/ndeigensystem-returns-incorrect-eigenvalues-for-2d-coulomb-problem-eigenfunctio I posted a similar question a short time ago regarding the 3D Coulomb problem. Jens’ excellent answer to this thread allowed me to obtain the correct eigenvalues and eigenenergies for that system. I ... - asked by Matthew Brunetti (10 votes), answered by Jens (12 votes) —————————- [RandomInteger: speed with long lists] http://mathematica.stackexchange.com/questions/114047/randominteger-speed-with-long-lists I noticed an interesting eﬀect with RandomInteger when looking at the time to create $$10^8$$ random integers. The following code lines all take about 0.5 seconds on a i7 Windows 64bit Laptop: ... - asked by Eisbar (9 votes), answered by Daniel Lichtblau (8 votes) —————————- [Creating Saveable-¿False notebooks] http://mathematica.stackexchange.com/questions/113858/creating-saveable-false-notebooks Bug introduced in 10.3 or earlier and persisting through 10.4.1 Reproduced on Windows 7, 10 I’m having diﬃculties with programmatic creation of non saveable notebooks on Windows with V10.4.1. ... - asked by Kuba (9 votes), answered by Kuba (7 votes) ================================== Greatest hits from previous weeks: ================================== [How to make use of Associations?] http://mathematica.stackexchange.com/questions/52393/how-to-make-use-of-associations I have been curious about it for long. Now that Mathematica 10 arrives, I think it’s time to ask the question: How the new Association data structure would be used to improve Mathematica programming? ... - asked by Yi Wang (109 votes), answered by Leonid Shifrin (127 votes) —————————- [What are the most common pitfalls awaiting new users?] http://mathematica.stackexchange.com/questions/18393/what-are-the-most-common-pitfalls-awaiting-new-users As you may already know, Mathematica is a wonderful piece of software. However, it has a few characteristics that tend to confuse new (and sometimes not-so-new) users. That can be clearly seen from ... - asked by Dr. belisarius (308 votes), answered by Michael E2 (177 votes) ================================== Can you answer these? ================================== [Integrate producing bad result] http://mathematica.stackexchange.com/questions/113791/integrate-producing-bad-result I noticed a bug in Mathematica. It computes incorrectly a deﬁnite integral Integrate[y* Sqrt[(l1^2 - y^2) (l2^2 - y^2)]/(a^2 - y^2), {y, 0, l1}, Assumptions -&gt; l2 &gt; a &gt; l1 &gt; 0] and ... - asked by user1765636 (3 votes) —————————- [FindPeaks error ” Expecting an image or graphics instead of”] http://mathematica.stackexchange.com/questions/113884/findpeaks-error-expecting-an-image-or-graphics-instead-of I’m running Mathematica 10.3.1.0 on windows 7 Professional Sp.1 when I try to use FindPeaks I keep getting the following error, even when trying the example in the documentation. I have done the ... - asked by Phymonkey (2 votes) —————————- [How can I set notebook’s options without opening it?] http://mathematica.stackexchange.com/questions/113816/how-can-i-set-notebooks-options-without-opening-it At present moment, to batch apply a change in a set of notebook I use a ”brute force”, rough, method: (* simple example *) setBackgroundBlue[notebookFileName_] := Module[ {tempNb}, tempNb = ... - asked by mitochondrial (3 votes) ### 5.36 Tuesday, April 26, 2016 ================================== Top new questions this week: ================================== [Writing a word with straight lines] http://mathematica.stackexchange.com/questions/113403/writing-a-word-with-straight-lines Here is an interesting way to write a word: (it is from a poster for the International Museum Day 2006; I believe it even won an award at an international design competition) by Boris Ljubicic. ... - asked by VividD (59 votes), answered by Martin Buttner (54 votes) —————————- [Numerical inverse Laplace-Hankel transform for a highly oscillatory function] http://mathematica.stackexchange.com/questions/113240/numerical-inverse-laplace-hankel-transform-for-a-highly-oscillatory-function When trying to reproduce the result of this paper about numerical solution of Lamb’s problem, I encountered the double integral (to be more precise, the 0-order inverse Hankel-Laplace transform) of a ... - asked by xzczd (11 votes) —————————- [Fitting Stradivari’s scroll] http://mathematica.stackexchange.com/questions/113273/fitting-stradivaris-scroll How can I ﬁnd the simplest curve that gives me a scroll like this? This is where I am at the moment and doing it by hand is becoming more and more cumbersome. First, take a drawing of the scroll ... - asked by tsuresuregusa (11 votes), answered by nikie (13 votes) —————————- [NDEigensystem cannot solve numerically the 3D Coulomb problem, while DSolve returns the right answer] http://mathematica.stackexchange.com/questions/113520/ndeigensystem-cannot-solve-numerically-the-3d-coulomb-problem-while-dsolve-retu After having derived by hand the eigenvalues and eigenfunctions for the 3D and 2D hydrogen atom, I want to solve the systems numerically using Mathematica. I need to do this because my next step is to ... - asked by Matthew Brunetti (9 votes), answered by user21 (4 votes) —————————- [Make the moon’s 3D gif] http://mathematica.stackexchange.com/questions/113217/make-the-moons-3d-gif How do I make the following gif I tried: moon = Import[ "https://upload.wikimedia.org/wikipedia/commons/f/f0/Full_Moon_as_Seen_From_Denmark.jpg"]; {r, g, b} = ColorSeparate[ImageResize[moon, ... - asked by vito (9 votes), answered by Kuba (13 votes) —————————- [How to generate this structure of a list without ‘While‘ and the like?] http://mathematica.stackexchange.com/questions/113307/how-to-generate-this-structure-of-a-list-without-while-and-the-like I need to create a list that holds, for given integer d, the elements $$1,\ldots ,d,d+2,\ldots ,2d,2d+3,\ldots ,3d,3d+4,\ldots ,d^2$$ where $$\ldots$$ is just denoting increment by 1 until the next written ... - asked by Lukas (8 votes), answered by ciao (3 votes) —————————- [Join a list with 6, 6, 2 dimensions with a list 6, 6 dimensions] http://mathematica.stackexchange.com/questions/113630/join-a-list-with-6-6-2-dimensions-with-a-list-6-6-dimensions listA = {{a1, a2, a3, a4, a5, a6}, {b1, b2, b3, b4, b5, b6}, {c1, c2, c3, c4, c5, c6}, {d1, d2, d3, d4, d5, d6}, {e1, e2, e3, e4, e5, e6}, {f1, f2, f3, f4, f5, f6}} listB = {{{n1, p1}, {n2, p2}, ... - asked by SPIL (7 votes), answered by Kuba (6 votes) ================================== Greatest hits from previous weeks: ================================== [How to plot an ellipse?] http://mathematica.stackexchange.com/questions/20100/how-to-plot-an-ellipse I’m new to Mathematica, and I’m ﬁnding it diﬃcult to plot an ellipse. I tried using Plot[(x/5)^2 + (y/3)^2 == 1, {x, -5, 5}, {y, -3, 3}] but I’m getting some errors. Is there something wrong ... - asked by Sriram (5 votes), answered by Jens (15 votes) —————————- [Multivariable Taylor expansion does not work as expected] http://mathematica.stackexchange.com/questions/15023/multivariable-taylor-expansion-does-not-work-as-expected The basic multivariable Taylor expansion formula around a point is as follows: - asked by matheorem (24 votes), answered by Jens (29 votes) ================================== Can you answer these? ================================== [JournalArticle does not react on the PointSize option] http://mathematica.stackexchange.com/questions/113547/journalarticle-does-not-react-on-the-pointsize-option The Default StyleSheet recognizes the PointSize option for ListPlot:  ListPlot[Table[Table[{i, j*i}, {i, 1, 10}], {j, 1, 3}], PlotStyle -&gt; {{Red, PointSize[0.1]}, {Blue, PointSize[0.05]}, ...  - asked by Alexei Boulbitch (2 votes) —————————- [How to trace the stylesheet directives responsible for the selected text’s appearance?] http://mathematica.stackexchange.com/questions/113495/how-to-trace-the-stylesheet-directives-responsible-for-the-selected-texts-appea By way of example, in a typical Mathematica interactive session, one sees text content as shown below: Three diﬀerent text styles can be seen in this ﬁgure: input, output, and the style for the ... - asked by kjo (5 votes) —————————- [How do I get my ZWO ASI120MM astro-camera to work in MMA?] http://mathematica.stackexchange.com/questions/113481/how-do-i-get-my-zwo-asi120mm-astro-camera-to-work-in-mma I am using Windows 10 + MMA 10.4.1. I bought a ZWO ASI120MM astro camera which I want to use as a guiding camera during astrophotography. From this site (http://astronomy-imaging-camera.com/software/) ... - asked by Max (2 votes) ### 5.37 Tuesday, April 19, 2016 ================================== Top new questions this week: ================================== [How to make this beautiful animation] http://mathematica.stackexchange.com/questions/112700/how-to-make-this-beautiful-animation How to make an animation of following gif in Mathematica? Edit: The animation shown above was created by Charlie Deck in processing. And how to make 3D analog? I tried ﬁrst few steps line = ... - asked by vito (36 votes), answered by C. E. (38 votes) —————————- [Can you plot pure function without specifying variable?] http://mathematica.stackexchange.com/questions/112478/can-you-plot-pure-function-without-specifying-variable Given a pure function, e.g. f=Sin[#]& it is possible to plot it with introducing an arbitrary local variable, e.g., Plot[f[x],x,0,1] However, the introduction of a variable x seems ... - asked by JeﬀDror (15 votes), answered by Jens (12 votes) —————————- [Vizualization of percolation paths] http://mathematica.stackexchange.com/questions/112878/vizualization-of-percolation-paths I did a simple demonstration to illustrate the percolation theory for my students. The content is a conductive square network possessing electrodes at its top and bottom edges. Some randomly chosen ... - asked by Alexei Boulbitch (13 votes), answered by Kuba (8 votes) —————————- [How to access FEM shape functions] http://mathematica.stackexchange.com/questions/112907/how-to-access-fem-shape-functions A couple of days ago I asked here about surface meshes and plotting on surfaces. Now I have another question: How can I access the surface or boundary element shape functions? I would like to ... - asked by AxelF (9 votes), answered by user21 (7 votes) —————————- [Finding peaks of curve with small values] http://mathematica.stackexchange.com/questions/112993/finding-peaks-of-curve-with-small-values I have 2d data of which I want to ﬁnd the peaks. data &lt;&lt; "http://pastebin.com/raw/EQFz1KFn"; peaks = FindPeaks[data[[All, 2]], 0, 0, -Infinity] // N The magnitudes of the found peaks are ... - asked by mrz (8 votes), answered by JasonB (11 votes) —————————- [Is there research about the Mathematica programming paradigm?] http://mathematica.stackexchange.com/questions/112920/is-there-research-about-the-mathematica-programming-paradigm There seem to be lots of papers discussing the functional programming paradigm terminology for Haskell, such as monad, category theory, lambda calculus, *morphism, etc. People study concepts and ... - asked by Eric (8 votes) —————————- [Constructing a graph from a distance matrix] http://mathematica.stackexchange.com/questions/112745/constructing-a-graph-from-a-distance-matrix I have a set $$S$$ of $$n$$ 2-dimensional points. We can compute a distance matrix (Euclidean distance) for $$S$$ using say this answer. I wish to form an $$n$$-vertex graph having the points $$S$$ as vertices, ... - asked by Juho (8 votes), answered by Martin Buttner (9 votes) ================================== Greatest hits from previous weeks: ================================== [Labeling individual curves in Mathematica] http://mathematica.stackexchange.com/questions/4444/labeling-individual-curves-in-mathematica I need to create a plot for export and inclusion in a report. Is there a better way to label curves than PlotLegends? From what I’ve read and my personal experience, PlotLegends is pretty bad. Is ... - asked by Tianxiang Xiong (42 votes), answered by Artes (36 votes) —————————- [What is the best Mathematica tutorial for young people?] http://mathematica.stackexchange.com/questions/733/what-is-the-best-mathematica-tutorial-for-young-people As Conrad Wolfram said at the TED conference, in the future kids should focus more on new technology. Computers compute better than humans, so we should focus more on thinking and getting the ... - asked by noisy (43 votes), answered by Vitaliy Kaurov (23 votes) ================================== Can you answer these? ================================== [Possible reduced GUI performance in 10.4] http://mathematica.stackexchange.com/questions/112526/possible-reduced-gui-performance-in-10-4 I have observed signiﬁcantly reduced performance in GUI in Mathematica v10.4. This is especially visible in autocomplete feature delays. This is very evident when I turn some power saving features ... - asked by leosenko (3 votes) —————————- [Why does Eigenvalues work for a matrix $$\{M\}$$ but not $$\{\{M\}\}$$?] http://mathematica.stackexchange.com/questions/112619/why-does-eigenvalues-work-for-a-matrix-m-but-not-m Suppose I have a matrix {{1, 2}, {3, 4}} which I’ll call mat. In a blur of human error, I computed the eigenvalues of mat with an extra set of curly braces surrounding it. To my surprise, this ... - asked by user170231 (3 votes) —————————- [Calculate the ESP Grid based on Density Grid] http://mathematica.stackexchange.com/questions/112872/calculate-the-esp-grid-based-on-density-grid I want to build a fast way to convert a density grid ﬁle into a grid ﬁle of the respective electrostatic potential (ESP; also known as MEP, the molecular electrostatic potential). This ... - asked by pH13 - Yet another Philipp (3 votes) ### 5.38 Tuesday, April 12, 2016 ================================== Top new questions this week: ================================== [How to model wooden joints with mathematica’s FEM?] http://mathematica.stackexchange.com/questions/111960/how-to-model-wooden-joints-with-mathematicas-fem This is a dovetail joint: and I’d like to see the stresses and deformation on the joint.I haven’t seen any modeling of disconnected regions with FEM, only connected regions, so I’m curious if you ... - asked by tsuresuregusa (16 votes), answered by user21 (6 votes) —————————- [Possible Bug in ArrayMesh] http://mathematica.stackexchange.com/questions/111945/possible-bug-in-arraymesh Suppose we have the following array from which we intend to create an ArrayMesh: arr = {{{1, 1, 1}, {1, 0, 1}, {1, 1, 0}}, {{1, 1, 1}, {0, 1, 1}, {1, 1, 0}}, {{0, 1, 0}, {0, 1, 1}, {0, 0, 1}}}; ... - asked by RunnyKine (15 votes), answered by ilian (9 votes) —————————- [How to draw all paths from (1,1) to (n,n) by move (+1, 0) or (0, +1)?] http://mathematica.stackexchange.com/questions/112395/how-to-draw-all-paths-from-1-1-to-n-n-by-move-1-0-or-0-1 Now I can draw some grid: But what I want(I’m sorry for the weird line. I have no image processing software in my mac...): Please notice: f(1, 1) = f(2, 1) = f(3, 1) = 1 f(1, 1) = f(1, 2) = ... - asked by Sayakiss (14 votes), answered by wxﬄes (14 votes) —————————- [All the food WolframAlpha knows about] http://mathematica.stackexchange.com/questions/112104/all-the-food-wolframalpha-knows-about I want to plot some nutritional values and do some computation with it. Is there an analogue of CountryData[] to get a list of all the foods for which WA has information? - asked by Andrea Di Biagio (12 votes), answered by C. E. (12 votes) —————————- [RegionNearest and neighborhoods] http://mathematica.stackexchange.com/questions/112264/regionnearest-and-neighborhoods In this previous question we see that RegionNearest isn’t quite as ’capable’ as Nearest for some things. Similarly, I need to be able to ﬁnd a given neighborhood of points on a MeshRegion. With ... - asked by ﬂip (11 votes), answered by Simon Woods (10 votes) —————————- [How do I extract a matrix of only positive numbers given a set of assumptions?] http://mathematica.stackexchange.com/questions/111989/how-do-i-extract-a-matrix-of-only-positive-numbers-given-a-set-of-assumptions I want to divide a matrix: mat = {{a, 0, -b}, {d, a, 0}, {0, 0, -a}} with the following assumptions: a &gt;= 0, b &gt;= 0, d &gt;= 0 Into two matrices, one containing the positive elements, and one ... - asked by Luis Fernando (11 votes), answered by b.gatessucks (14 votes) —————————- [How to type text with an underbrace underneath it like: $$\underbrace {g...g}_{n-times}$$?] http://mathematica.stackexchange.com/questions/111970/how-to-type-text-with-an-underbrace-underneath-it-like-underbraceg-g-n-t I want to use the underbrace ”esc u esc” but have it placed underneath text. Like in a mathematica text cell. Is it possible? Thanks - asked by Craig (11 votes), answered by JasonB (16 votes) ================================== Greatest hits from previous weeks: ================================== [How to plot an ellipse?] http://mathematica.stackexchange.com/questions/20100/how-to-plot-an-ellipse I’m new to Mathematica, and I’m ﬁnding it diﬃcult to plot an ellipse. I tried using Plot[(x/5)^2 + (y/3)^2 == 1, {x, -5, 5}, {y, -3, 3}] but I’m getting some errors. Is there something wrong ... - asked by Sriram (5 votes), answered by Jens (15 votes) —————————- [How to manipulate 2D plots?] http://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 Istvan Zachar (94 votes), answered by Istvan Zachar (105 votes) ================================== Can you answer these? ================================== [Possible Bug in LinearSolveFunction with Sparse Vectors] http://mathematica.stackexchange.com/questions/112313/possible-bug-in-linearsolvefunction-with-sparse-vectors Bug introduced in 5.0 and persists through 10.4 LinearSolveFunction is new in 5.0 Consider the following set of equations and corresponding variables: eqns1 ={2 x == 2 - 4 y, 3 y == 4 z, 2 z + 4 ... - asked by RunnyKine (8 votes) —————————- [Why FoldList 5 times faster than Apply for matrix multiplication?] http://mathematica.stackexchange.com/questions/112125/why-foldlist-5-times-faster-than-apply-for-matrix-multiplication Consider this list of $$2x2$$ matrices: list=RandomReal[{-2,2},{500,2,2}]; Now compare timings of Apply and FoldList for matrix multiplication: t1=FoldList[Dot,list];//AbsoluteTiming (* 0.000324, ... - asked by Lukas (6 votes) —————————- [Generating OpenCL C code] http://mathematica.stackexchange.com/questions/112127/generating-opencl-c-code I’m trying to make an interactive complex function plotter using OpenCl. So far I can only plot functions that I hardcode into the kernel by hand. I’d like to be able to use ComplexExpand@#@f@(x + ... - asked by ra91 (6 votes) ### 5.39 Tuesday, April 5, 2016 ================================== Top new questions this week: ================================== [Rounding the Corners of a Shape] http://mathematica.stackexchange.com/questions/111479/rounding-the-corners-of-a-shape I was wondering whether there is an option in Mathematica that enables me to smooth the corners of a shape. The example I want to start with is the pentagon. This can be crudely speciﬁed as ... - asked by Mr S 100 (23 votes), answered by MarcoB (21 votes) —————————- [Writing functions with ”Method” options] http://mathematica.stackexchange.com/questions/111666/writing-functions-with-method-options I’d like to implement several behaviors for a particular function using a Method option added to the function deﬁnition: Options[saveData] = {Method -&gt; "Addition"}; saveData[vars_, opts : ... - asked by dionys (14 votes), answered by Shutao TANG (7 votes) —————————- [Interpretation of the result of ?@] http://mathematica.stackexchange.com/questions/111394/interpretation-of-the-result-of This might be a very trivial question but as a beginner, I don’t know the answer. I was exploring ? and after running a cell containing ?@, I got an interesting result: However, I’m not sure about ... - asked by MathX (13 votes), answered by m_goldberg (15 votes) —————————- [Ticks in v10 - a bug or undocumented change] http://mathematica.stackexchange.com/questions/111663/ticks-in-v10-a-bug-or-undocumented-change Bug introduced in 10.0 and ﬁxed in 10.4 In this post @Heike provides this code: ticksfun[xmin_, xmax_] := Table[{10^i, Superscript[10, i]}, {i, Floor[Log10[xmin]], Ceiling[Log10[xmax]]}] ... - asked by leosenko (12 votes), answered by rcollyer (8 votes) —————————- [Why is an empty list not tested by VectorQ?] http://mathematica.stackexchange.com/questions/111438/why-is-an-empty-list-not-tested-by-vectorq I am a bit amazed by this behavior of VectorQ[ expr, test ]: VectorQ[ {}, NumberQ ] True It seems that the test itself is never applied and thus does not matter, so NumericQ or OddQ for ... - asked by gwr (11 votes), answered by Szabolcs (16 votes) —————————- [Matrix indexed by one number] http://mathematica.stackexchange.com/questions/111631/matrix-indexed-by-one-number I’m trying to ﬁnd a generic way (for arbitrary dimensions) to create a matrix like so a[1] a[2] a[3] a[4] i.e where it is indexed by one number, instead of say Array[a, 2, 2] which gives ... - asked by Henrik (10 votes), answered by Szabolcs (14 votes) —————————- [ErrorListPlot ignores some exact data points] http://mathematica.stackexchange.com/questions/111436/errorlistplot-ignores-some-exact-data-points Possible bug? Or am I missing something / expecting too much? Forgive the seemingly obscure data points but they’re where I’ve noticed a problem. Needs["ErrorBarPlots"] data = { {{(10 Pi)/8, 1}, ... - asked by Quantum_Oli (9 votes) ================================== Greatest hits from previous weeks: ================================== [Generate two random numbers with constraints] http://mathematica.stackexchange.com/questions/97424/generate-two-random-numbers-with-constraints I want to generate two random numbers, $$p$$ and $$q$$, between $$0.5$$ and $$1$$. They are connected by the constraint $$1/(2q) > p$$. How do I generate $$p$$ and $$q$$? - asked by Chandan Datta (25 votes), answered by JasonB (11 votes) —————————- [Multivariable Taylor expansion does not work as expected] http://mathematica.stackexchange.com/questions/15023/multivariable-taylor-expansion-does-not-work-as-expected The basic multivariable Taylor expansion formula around a point is as follows: \[ f(\mathbf r + \mathbf a) = f(\mathbf r) + (\mathbf a \cdot \nabla )f(\mathbf r) + \frac {1}{2!}(\mathbf a \cdot \nabla )^2 f(\mathbf r) + \cdots

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

[Numerical Optimal Control] http://mathematica.stackexchange.com/questions/111375/numerical-optimal-control

It seems that most practical optimal control problems are only able to be solved numerically using a non-linear programming approach. As such, I was hoping to tackle the following optimal control ...

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[How to deﬁne a custom 3D graphics primitive in Mathematica?] http://mathematica.stackexchange.com/questions/111403/how-to-define-a-custom-3d-graphics-primitive-in-mathematica

There are lots of basic graphics pimitive in Mathematica such as 2D- caseLine[], Circle[] and 3D case Cylinder[], BSplineSurface[],etc.

In general, they own the following usage if memory serves:

...

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[Can Mathematica reliably determine the equality of any two constructible numbers?] http://mathematica.stackexchange.com/questions/111615/can-mathematica-reliably-determine-the-equality-of-any-two-constructible-numbers

A constructible number is any number which can be expressed with only natural numbers and the operators $$+$$, $$-$$, $$\times$$, $$/$$, $$\sqrt {}$$ (square root only). Is Mathematica’s Simplify or FullSimplify ...

### 5.40 Tuesday, March 29, 2016

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

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

The ﬁgure is

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

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

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[Is there a simple strategy to determine whether a point is inside a boundary?] http://mathematica.stackexchange.com/questions/111114/is-there-a-simple-strategy-to-determine-whether-a-point-is-inside-a-boundary

For a ellipse $$E(\theta )$$, which owns the parametric equation as follows:

$$\begin {cases} x = a \sin \theta + b \cos \theta + c \\ y = d \sin \theta + e \cos \theta + f \\ \end {cases}$$

Now, I have a ...

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[How to divide the wine into two equal portions] http://mathematica.stackexchange.com/questions/111250/how-to-divide-the-wine-into-two-equal-portions

There is a 8-liter bottle is full of wine. There are two empty bottles that have capacity 5-liters and 3-liters. How can these three bottles be used to separate the wine into two 4-liter portions?

...

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[solve this probability problem symbolically] http://mathematica.stackexchange.com/questions/110789/solve-this-probability-problem-symbolically

Consider a unit square, Pick two points P and Q uniformly at random inside the square, What is the probability that —PQ—¿1?

I tried solve this problem

...

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I have tried to rewrite my old IDL code to calculate the radial correlation function for a regular 2D crystal structure.

The theory behind this function is given here: ...

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[How to plot GDPs in this way?] http://mathematica.stackexchange.com/questions/110901/how-to-plot-gdps-in-this-way

Actually the current answer is very wonderfull.The bouns just for someone can complete this question.

I found this interesting plot of how the relationship between the GDPs of diﬀerent countries has ...

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[Interesting Progression of ParametricRegion: Bug?] http://mathematica.stackexchange.com/questions/110791/interesting-progression-of-parametricregion-bug

Consider the following ParametricRegion from an answer to this question:

region = ParametricRegion[{{(1 + r - 12 r^2 + 4 r^3)/(2 r - 2),
z Sqrt[(4 r^2)/(r - 1)^2 (r - r^2 (r - 3)^2)]},
2  ...

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

[How do I clear all user deﬁned symbols?] http://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?

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[How to create word clouds?] http://mathematica.stackexchange.com/questions/2334/how-to-create-word-clouds

Word clouds are rather useless fancy and visually appealing plots, where words are plotted with diﬀerent sizes according to their frequency in a corpus. Many applications exist out there (Wordle, ...

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

[Overlay Inside a Grid/Column/Row Not Working] http://mathematica.stackexchange.com/questions/110836/overlay-inside-a-grid-column-row-not-working

Here is a microscopy image of some cells I want to make measurements on with Mathematica:

In order to make some measurements of cells in a microscopy image I have written a simple dynamic overlay ...

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Please see code snippet below - I have a weighted, connected graph that models a software process using a DiscreteMarkovProcess. I set some of the edge weights to zero to ”turn oﬀ” some of the ...

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[Counting automorphisms that preserve a group action] http://mathematica.stackexchange.com/questions/111102/counting-automorphisms-that-preserve-a-group-action

Note: the math, I believe, is not the problem here. The issue is not that I get the wrong answer, just that my code does not terminate. So, if you do not feel comfortable with the problem below, I do ...

### 5.41 Tuesday, March 22, 2016

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

[General techniques for creating complex animations] http://mathematica.stackexchange.com/questions/110190/general-techniques-for-creating-complex-animations

I love good animations of abstract concepts, and when I try to create them myself, I prefer doing so in code to make sure they are exact (and because some things are just way too ﬁddly to do by ...

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[Is there a numerical method/built-in to calculate the boundary of a set of graphs?] http://mathematica.stackexchange.com/questions/110236/is-there-a-numerical-method-built-in-to-calculate-the-boundary-of-a-set-of-graph

Recently, I encounted a geometry problem in my work. For a curve-family that owns the following parametric equation:

...

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[Creating 3D dice] http://mathematica.stackexchange.com/questions/110295/creating-3d-dice

How to create an image of a 3D die from the 2D images?

There is an example in the Documentation Center

I tried

but it doesn’t work.

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[Regression /Bug in DelaunayMesh from 10.3.1 to 10.4] http://mathematica.stackexchange.com/questions/110598/regression-bug-in-delaunaymesh-from-10-3-1-to-10-4

In answering this question, I realized the OP and I were obtaining diﬀerent results from the alphaShapes2D code. This question was updated with additional point sets, but when I tried to use my ...

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[Handling Kernel quit] http://mathematica.stackexchange.com/questions/110162/handling-kernel-quit

One can use $Epilog to do something when the Kernel is quit or put an end.m ﬁle next to the init.m. For Wolfram System sessions,$Epilog is conventionally deﬁned to read in a ﬁle named end.m.

...

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[What is the closest star to Earth other than the sun?] http://mathematica.stackexchange.com/questions/110559/what-is-the-closest-star-to-earth-other-than-the-sun

How to ﬁnd the Sun’s nearest neighbor star using Mathematica? I tried

but it didn’t work

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[Find the Panda - Dudolf panda puzzle] http://mathematica.stackexchange.com/questions/110497/find-the-panda-dudolf-panda-puzzle

I recently ﬁnd this puzzle where you have to ﬁnd the panda from a group of snowmen. Having a horrible eyesight I have to take help of mathematica to ﬁnd it.

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

[How to make use of Associations?] http://mathematica.stackexchange.com/questions/52393/how-to-make-use-of-associations

I have been curious about it for long. Now that Mathematica 10 arrives, I think it’s time to ask the question: How the new Association data structure would be used to improve Mathematica programming?

...

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[Mathematica 10.0.x freezes in Initializing kernels] http://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 ...

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

Bug introduced in 6.0 and persisting through 10.4

SiegelTheta is new in 6.0

In order to test the SiegelTheta function, I wanted to evaluate it for $$\mathbf s=\mathbf 0$$ when $$\mathbf ...$$

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[How do I invert a function with two arguments?] http://mathematica.stackexchange.com/questions/110146/how-do-i-invert-a-function-with-two-arguments

I begin with a function deﬁned by

c[u_, mH_]

I won’t go into details because it comes from countless lines of partial diﬀerential equations, boundary conditions and perturbations. But suﬃce to ...

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[Cell format for usage statements] http://mathematica.stackexchange.com/questions/110199/cell-format-for-usage-statements

The myFunc::usage statement is intended to be a simple summary of the symbol and its arguments. However, many users like myself opt out of using Workbench and prefer to maximize use of the Notebook ...

### 5.42 Tuesday, March 15, 2016

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

[General strategies to write big code in Mathematica?] http://mathematica.stackexchange.com/questions/109888/general-strategies-to-write-big-code-in-mathematica

I think after six months of exposure to Mathematica and the Wolfram Language I am fairly OK with writing short codes and snippets. However, what are some general strategies to use in order to write ...

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[How to make the digits of Pi go around in a spiral like this?] http://mathematica.stackexchange.com/questions/109982/how-to-make-the-digits-of-%cf%80-go-around-in-a-spiral-like-this

Here is a start.

MapIndexed[Text[Reverse[First[RealDigits[Pi,10,252]]][[Tr@#2]],#]&amp;,
Table[{t Cos[t],t Sin[t]},{t,0,16Pi,0.2}]]//Graphics

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[Guidelines for planning custom GUI in Mathematica] http://mathematica.stackexchange.com/questions/109525/guidelines-for-planning-custom-gui-in-mathematica

Intro

Usually I don’t have to care (it hurts my brain though) about misaligned details, additional/missing pixels. But currently I’m participating in a project where the design matters and I have to ...

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[Wrong labelling of contours with ListContourPlot] http://mathematica.stackexchange.com/questions/109778/wrong-labelling-of-contours-with-listcontourplot

Bug introduced in 9.0 or earlier and persisting through 10.4

Consider this example:

dat = Table[Re[Sqrt[1 - x^2 - y^2]], {x, -1.1, 1.1, 0.01}, {y, -1.1, 1.1, 0.01}];

Now pay special attention to ...

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[Fit image of mountain to gaussian] http://mathematica.stackexchange.com/questions/109946/fit-image-of-mountain-to-gaussian

I want to detect the edges of an image of a mountain and then ﬁt that to a gaussian.

I am unsure about how to only get the mountain edge, rather than every single edge in the image.

How do I ...

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[What is a printer’s point?] http://mathematica.stackexchange.com/questions/109813/what-is-a-printers-point

According to the documentation it is a basic unit for size spec. WindowSize and ImageSize says:

I think all the statements below are correct yet I would like to know for sure:

Is this the same ...

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[A weird issue with Interval[$MaxNumber]] http://mathematica.stackexchange.com/questions/109597/a-weird-issue-with-intervalmaxnumber From the Interval documentation: For approximate machine- or arbitrary-precision numbers x, Interval[x] yields an interval reﬂecting the uncertainty in x. $Version
(* 10.4.0 for Microsoft  ...

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

[What is the best Mathematica tutorial for young people?] http://mathematica.stackexchange.com/questions/733/what-is-the-best-mathematica-tutorial-for-young-people

As Conrad Wolfram said at the TED conference, in the future kids should focus more on new technology. Computers compute better than humans, so we should focus more on thinking and getting the ...

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[Is Mathematica worth it for me?] http://mathematica.stackexchange.com/questions/100072/is-mathematica-worth-it-for-me

I’m 13 years old and in 7th grade. I’m currently in Algebra 1, and I have fallen in love with both math and programming.

When I came upon Mathematica, it was awesome. My two favorite things fused ...

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

[Building a classiﬁer for images] http://mathematica.stackexchange.com/questions/109484/building-a-classifier-for-images

I tried to build a classiﬁer for some images that I have with the following code:

class1 = Import /@
FileNames["*",
"location1"];

class2 = Import /@
FileNames["*",
"location2"];

...

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[AppearanceRules on multipage Web Form] http://mathematica.stackexchange.com/questions/109887/appearancerules-on-multipage-web-form

I’m attempting to make a web survey using FormFunction. To list the questions I am using AppearanceRules to give each page an individual title. I can’t ﬁnd any documentation in regards to ...

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I would like a function that computes Cartesian product of two
sets z=(Tuples@{#1,#2}), and computes the number of elements in this set(list)
Length@z which have a x elements in #1 and y elements in  ...

### 5.43 Tuesday, March 8, 2016

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

[How to design CloudObjects with reasonable CloudCredit costs] http://mathematica.stackexchange.com/questions/109259/how-to-design-cloudobjects-with-reasonable-cloudcredit-costs

Note: I originally thought to post this as a non-answer/extended comment to this question; however I feared that I would end up hijacking the original question. It is likely a duplicate with the ...

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[How to merge two screenshots into one image?] http://mathematica.stackexchange.com/questions/109196/how-to-merge-two-screenshots-into-one-image

I have two screenshots:

For a long screenshot picture I usually use PhotoShop to combine both images:

How do I use Mathematica to make an automated program to do this? This is my current ...

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[Current (e.g., ca. 2016 / MMa 10 / WP 4+) best practices for embedding interactive content in WordPress?] http://mathematica.stackexchange.com/questions/109231/current-e-g-ca-2016-mma-10-wp-4-best-practices-for-embedding-interacti

My strategy, in the past, has been to embed interactive CDF ﬁles into my WordPress blog for student’s to use (Much like the Wolfram Demonstration Project).

As many know 1) the ’Plug in’ ...

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[Getting data from FRED] http://mathematica.stackexchange.com/questions/109203/getting-data-from-fred

Mathematica V10.4 supports a service for connection to FRED. If you create a connection with

fred = ServiceConnect["FederalReserveEconomicData"]

(you need to have created a login id to be ...

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[Do[ ]s and Don’t[ ]s when teaching Mathematica in undergraduate courses] http://mathematica.stackexchange.com/questions/108987/do-s-and-dont-s-when-teaching-mathematica-in-undergraduate-courses

Question motivated by some horriﬁc homework-related posts that I don’t dare to link:

What are the top Do’s and Dont’s when teaching Mathematica to undergrads?

I don’t ask for the design of a ...

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[Primes Race (Mathematica Eﬃciency)] http://mathematica.stackexchange.com/questions/108798/primes-race-mathematica-efficiency

I am currently working with a paper that deals with this concept of Prime Races. You essentially create a large list of prime numbers and then split that list into two teams. You are assigned to ...

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[Gathering of list] http://mathematica.stackexchange.com/questions/109104/gathering-of-list

Problem statement

The following challenge was recently posted to the J language programming forum by Skip Cave http://jsoftware.com/pipermail/programming/2016-March/044561.html

”The animal ...

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

[Find eigen energies of time-independent Schrodinger equation] http://mathematica.stackexchange.com/questions/32293/find-eigen-energies-of-time-independent-schr%c3%b6dinger-equation

I’m trying to get the eigenvalues of a one dimensional time-independent Schrodinger equation,

$$-\frac {h^2}{2m_0}\frac {d^2\psi }{dx^2}+U(x)~\psi =Ei~\psi$$

where U(x) is some potential and Ei is the ...

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[How to plot an ellipse?] http://mathematica.stackexchange.com/questions/20100/how-to-plot-an-ellipse

I’m new to Mathematica, and I’m ﬁnding it diﬃcult to plot an ellipse. I tried using

Plot[(x/5)^2 + (y/3)^2 == 1, {x, -5, 5}, {y, -3, 3}]

but I’m getting some errors. Is there something wrong ...

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

[Mimicking Console and Output Matlab/Rstudio-Style Environment in Mathematica?] http://mathematica.stackexchange.com/questions/109179/mimicking-console-and-output-matlab-rstudio-style-environment-in-mathematica

I am trying to crudely approximate the RStudio or Matlab Workspace environment in Mathematica by having a speciﬁc notebook function as the ”console notebook” where I execute commands and another ...

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[What is the equivalent of $ModuleNumber for DynamicModule] http://mathematica.stackexchange.com/questions/108850/what-is-the-equivalent-of-modulenumber-for-dynamicmodule Mathematica provides access to$ModuleNumber which can be enormously useful.

Unfortunately I can’t ﬁnd the equivalent for DynamicModule.

I know such a parameter must exist for two reasons:

First, ...

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[Why this expression is not evaluated correctly?] http://mathematica.stackexchange.com/questions/109310/why-this-expression-is-not-evaluated-correctly

Look at the following code:

f[kx_, ky_] := -1*(Exp[I*kx] + 2*Exp[-I*kx/2]*Cos[Sqrt[3]*ky/2]);
H = {{1, f[kx, ky]}, {Conjugate[f[kx, ky]], -1}};
D[Norm[Normalize[Eigensystem[H][[2]][[1]]]], kx] /. {kx  ...

- asked by Chong Wang (1 vote)

### 5.44 Tuesday, March 1, 2016

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

[Typoglycemia text manipulation] http://mathematica.stackexchange.com/questions/108563/typoglycemia-text-manipulation

I was just reading the article: https://en.wikipedia.org/wiki/Typoglycemia

”... readers can understand the meaning of words in a sentence even when the interior letters of each word are scrambled ...

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[Version inconsistency with optional arguments: what if the default value doesn’t match the pattern?] http://mathematica.stackexchange.com/questions/108636/version-inconsistency-with-optional-arguments-what-if-the-default-value-doesnt

I just came across some weird behaviour. Take this function deﬁnition:

ClearAll[f]
f[vs_List : All] := "match"

The default value of vs is All. Now think about what f[] should return. Should it ...

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[Reproducing a ranking function that behaves like Excel’s RANK] http://mathematica.stackexchange.com/questions/108309/reproducing-a-ranking-function-that-behaves-like-excels-rank

I tried to ﬁnd a function or expression in Mathematica that produces the same output as the RANK function in Excel (see its description here), but unfortunately I could not ﬁnd an existing one.

For ...

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[Given a large binary matrix, ﬁnd the largest submatrix containing non-zero elements] http://mathematica.stackexchange.com/questions/108299/given-a-large-binary-matrix-find-the-largest-submatrix-containing-non-zero-elem

I’m looking for a way to reduce a binary matrix containing zeros at some positions into a matrix that contains no zeros by deleting rows and columns of the original matrix until only non-zero values ...

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[Generating a list of numbers that are not multiples of 4] http://mathematica.stackexchange.com/questions/108502/generating-a-list-of-numbers-that-are-not-multiples-of-4

I want to write simple code that will list all numbers from $$1$$ to $$n$$ that are not multiples of $$4$$.

And in this case I consider that

n=100

For[i = 1, i &lt;= n, i++, If[Mod[i, 4] != 0,  ...

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[Can Mathematica convert a RegularExpression into a StringExpression or vice-versa?] http://mathematica.stackexchange.com/questions/108481/can-mathematica-convert-a-regularexpression-into-a-stringexpression-or-vice-vers

I know that Mathematica can perform string comparison using either StringExpression or RegularExpression. Although regular expressions are more common, I feel that the Mathematica StringExpressions ...

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[What options and settings can be used to create print quality typeset documents with Mathematica?] http://mathematica.stackexchange.com/questions/108553/what-options-and-settings-can-be-used-to-create-print-quality-typeset-documents

If I am proﬁcient on dedicated typesetting software (e.g. LaTeX) it makes sense to use that for typesetting but if I am not how can I use Mathematica to create good quality documents.

The question ...

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

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

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

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

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[Generating a Sierpinski carpet] http://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? ==================================

[Prepending a sequence with zeros gives ‘FindGeneratingFunction‘ hard time] http://mathematica.stackexchange.com/questions/108451/prepending-a-sequence-with-zeros-gives-findgeneratingfunction-hard-time

FindGeneratingFunction[{1, 3, 11, 43, 171, 683, 2731, 10923, 43691, 174763}, t]

gives the answer (namely (1 - 2 t)/(1 - 5 t + 4 t^2)) almost immediately.
However if I prepend zeros in  ...

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[Obtaining a Previously Constructed Function as Desired Output] http://mathematica.stackexchange.com/questions/108373/obtaining-a-previously-constructed-function-as-desired-output

I was playing around with some Generalized Trigonometric Functions deﬁned as follows;

 w[n_] := E^((2*\[Pi]*I)/n)

Ncos[n_, x_] := Expand[(1/n)*Sum[E^(x*w[2 n]^(2 k + 1)), {k, 0, n - 1}]]

...

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[The implementation of FunctionRange] http://mathematica.stackexchange.com/questions/108308/the-implementation-of-functionrange

How exactly does the FunctionRange work? What kind of algorithm does it use? I looked it up in the manual but it doesn’t provide any references or even a name of the algorithm.

It also accepts a ...

### 5.45 Tuesday, February 23, 2016

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

[++ is dangerous for C programmers] http://mathematica.stackexchange.com/questions/107619/is-dangerous-for-c-programmers

I noticed this fact, that may be misleading for programmers used to C language.

In Mathematica, if you have a function f[] and an array v, and you write

v[[ f[] ]]++

the function f is called ...

[Apply multiple functions to same list] http://mathematica.stackexchange.com/questions/107721/apply-multiple-functions-to-same-list

I’d like to get the Min, Max, Median, Mean, etc. for the same list. For now I’m doing the following:

y = {1, 2, 3, 4, 5, 6, 7};
Map[{Max[#] , Min[#] , Median[#], Mean[#]} &amp;, y, {0}]

It seems ...

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[How do I delete all items that occur more than once?] http://mathematica.stackexchange.com/questions/107483/how-do-i-delete-all-items-that-occur-more-than-once

DeleteDuplicates works fine but leaves a single copy of the duplicated item.
I need to remove all items that occur more than once i.e.
{{1,2},{1,2},{3,4}} -> {3,4}. There must be a one-liner.

[Puzzle with Mathematica] http://mathematica.stackexchange.com/questions/107859/puzzle-with-mathematica

Hello everyone, This is a puzzle I got from someone via social media. Basically, we need to ﬁll up the boxes with the numbers 1-9 (no repetitions) that ﬁt the multiplication and addition ...

[Finite Element Method and ElementMeshInterpolation issue in v10.3] http://mathematica.stackexchange.com/questions/107668/finite-element-method-and-elementmeshinterpolation-issue-in-v10-3

I recently installed Mathematica v10.3 and checked a project I was working on few months ago under Mathematica v10.1.

In this project I solve a PDE with NDSolve and Finite Element Method over a 2D ...

[Eﬃcient way to make subsets of list with placeholders] http://mathematica.stackexchange.com/questions/107517/efficient-way-to-make-subsets-of-list-with-placeholders

I have an arbitrary list of unique elements:

lst = {a, b, c, d}

Documentation allows finding subsets with same number of elements, say 2:

Subsets[lst, {2}]
(* {{a, b}, {a, c}, {a, d}, {b, c}, {b,  ...

[Double Sum Involving Condition] http://mathematica.stackexchange.com/questions/107652/double-sum-involving-condition

I would like to compute the dimensions of some small free nilpotent Lie algebras. However, I am totally new to this and I could not ﬁgure out how to write the double sum which gives the dimension of ...

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

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

According to the Mathematica help: Round rounds numbers of the form x.5 toward the nearest even integer.

For example:

Round[0.5, 1.5, 2.5, 3.5, 4.5]

gives

0, 2, 2, 4, 4

What’s the ...

[Calling Correct Function for Plotting DiracDelta] http://mathematica.stackexchange.com/questions/3506/calling-correct-function-for-plotting-diracdelta

I am wondering what is the correct function in Mathematica to plot the true impulse function, better known as the DiracDelta[] function. When using this inside of a function or just the function ...

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

[How many clusters does DominantColors return?] http://mathematica.stackexchange.com/questions/107842/how-many-clusters-does-dominantcolors-return

Is there any documentation on how it automatically chooses the number of colors - does it use X-means?

[Using GNU Make to compile MathLink program automatically removes a ﬁle] http://mathematica.stackexchange.com/questions/107863/using-gnu-make-to-compile-mathlink-program-automatically-removes-a-file

It’s possible that this question belongs on Stackoverﬂow; however, the Mathematica context may be important so I’m asking here ﬁrst.

I am working on a project to interact with sensors connected to ...

- asked by bobthechemist (1 vote)

[Why does Solve work in v9.0.1 but not in v10.3.1] http://mathematica.stackexchange.com/questions/107585/why-does-solve-work-in-v9-0-1-but-not-in-v10-3-1

I want to solve the following DE

The Mathematica command is

sol1 = DSolve[P'[t] == k (M - P[t]) P[t], P[t], t]

P[t_] = sol1[[1,1,2]]

sol2 ...

### 5.46 Tuesday, February 16, 2016

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

[Why does Mathematica report that $$\int _1^\infty \frac {\sin (\sqrt {x})}{\sqrt {x}}dx$$ = $$2\cos (1)$$?] http://mathematica.stackexchange.com/questions/106162/why-does-mathematica-report-that-int-1-infty-frac-sin-sqrtx-sqrtxdx

Bug introduced in 7.0 or earlier and persisting through 10.3.1 or later

Mathematica 10 gives the following very odd result,

Integrate[Sin[Sqrt[x]]/Sqrt[x], {x, 1, Infinity}]
(* 2 Cos[1] *)

which seems ...

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[How was Mathematica built?] http://mathematica.stackexchange.com/questions/106020/how-was-mathematica-built

I’ve been wondering this for a while now: How was Mathematica built?

Is it written in Haskell? C++? I’d love to get a taste of the wizardry behind this incredible software.

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[How can one manually change the rule ordering] http://mathematica.stackexchange.com/questions/106068/how-can-one-manually-change-the-rule-ordering

I have a function which has some general behaviour, but that should act on some speciﬁc kinds of objects in some other way. I know that Mathematica is supposed to automatically order the rules so ...

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[What governs images resizing in the FrontEnd environment] http://mathematica.stackexchange.com/questions/106204/what-governs-images-resizing-in-the-frontend-environment

What is responsible for the middle Row images’ size? And why single image row is diﬀerent?

{#, Row[{#, #}], Row[{#}]} &amp; @ RandomImage[1, {100, 100}]

I know I can prevent that with mapping ...

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[How to report a bug in Mathematica] http://mathematica.stackexchange.com/questions/106227/how-to-report-a-bug-in-mathematica

I found two bugs in Mathematica (10.3 and 10.1) and I need to report it. Is there any tools to do that or section on Wolfram website?

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[Reproduce image eﬀect in Mathematica] http://mathematica.stackexchange.com/questions/106165/reproduce-image-effect-in-mathematica

How do I create the ”dotifying” eﬀect below in Mathematica?

I have tried to use Rasterize ﬁrst to get the image pixelated, but how do I get the disc/circle pattern then?

image :=  ...

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[How to make a Cahn–Hilliard model GIF] http://mathematica.stackexchange.com/questions/106333/how-to-make-a-cahn-hilliard-model-gif

The question derived from @Jason B ’s answer.I wanna make it but don’t how to do. But we can get some rule about the GIF

The change of the total pixel is very small.

imagelist =  ...

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

[Generating visually pleasing circle packs] http://mathematica.stackexchange.com/questions/40334/generating-visually-pleasing-circle-packs

EDIT: (my conclusion and thank you note) I want to thank you all guys for this unexpected intellectual and artistic journey. Hope you had fun and enjoyed it the same as I did.

I would like to ...

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[How to calculate contour integrals with Mathematica?] http://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?

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

[Extracting control points from BezierFunction] http://mathematica.stackexchange.com/questions/107435/extracting-control-points-from-bezierfunction

given a Bezier surface, is there a simple way to express $$g_{12}$$ (from the First fundamental form) again in Bezier form?

More precisely, I have control points and a Bezier function $$f$$:

cps = {{{0,  ...

- asked by Osmihran (1 vote)

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[Order of importing data from ﬁles] http://mathematica.stackexchange.com/questions/106296/order-of-importing-data-from-files

I have many text ﬁles numbered from 1 to 1 million in numerical order. Within each text ﬁle is 5 columns of data (TAB spaced) with many rows. I eﬀectively want to take the minimum value from each ...

- asked by David (1 vote)

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[WolframScript Unix - Script Parameters on Raspberry Pi] http://mathematica.stackexchange.com/questions/107436/wolframscript-unix-script-parameters-on-raspberry-pi

I’m currently trying to run a script with 2 parameters which gets called via a BASH script. The script runs ﬁne however the list of passed parameters , \$ScriptCommandLine, always stays empty.

...

### 5.47 Tuesday, February 9, 2016

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

[Partitioning a list when the cumulative sum exceeds 1] http://mathematica.stackexchange.com/questions/105792/partitioning-a-list-when-the-cumulative-sum-exceeds-1

I have a long list of say 1 million Uniform(0,1) random numbers, such as:

 dat = {0.71, 0.685, 0.16, 0.82, 0.73, 0.44, 0.89, 0.02, 0.47, 0.65}

I want to partition this list whenever the cumulative ...

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[How to extract a contour line (or a region) from a ContourPlot?] http://mathematica.stackexchange.com/questions/105750/how-to-extract-a-contour-line-or-a-region-from-a-contourplot

Given a ContourPlot with a set of contours, say, this:

is it possible to get the contours separating domains with the diﬀerent colors in the form of lists?

For example, how to extract the ...

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[Using NDSolve to ﬁnd particle trajectory] http://mathematica.stackexchange.com/questions/105859/using-ndsolve-to-find-particle-trajectory

I’m trying to simulate a particle in an electric and magnetic ﬁelds, but numerically instead of analytically. This is basically solving the equation

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[why MatchQ is fast and Replace slow?] http://mathematica.stackexchange.com/questions/105626/why-matchq-is-fast-and-replace-slow

Consider a large expression, say a polynomial with 25 terms

expr=Product[Unique["a"],{i,1,25}];

to which you apply the following replacement rule:

rep={x_ f[y_] /; FreeQ[x, y] -&gt; 0};

Since f ...

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[Use of some functions of the Developer Utility Package, such as BesselSimplify] http://mathematica.stackexchange.com/questions/105643/use-of-some-functions-of-the-developer-utility-package-such-as-besselsimplify

The Developer Utilities Package contains several functions that look interesting:

BesselSimplify
GammaSimplify
PolyGammaSimplify
ZetaSimplify
PolyLogSimplify
and TrigToRadicals

However for each ...

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[Plot of $$sin(x^x)$$ is missing from $$x=143$$] http://mathematica.stackexchange.com/questions/105774/plot-of-sinxx-is-missing-from-x-143

When plotting the graph of $$\sin (x^x)$$ I noticed that there is no plot from about $$x=143$$. I don’t suppose there is a purely mathematical explanation for this?

So, why is there no graph in ...

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[Brackets around each item in matrix] http://mathematica.stackexchange.com/questions/105864/brackets-around-each-item-in-matrix

I have a matrix where every item in the matrix has its own brackets that I do not want. How can I remove the brackets around each item?

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

[How do I clear all user deﬁned symbols?] http://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?

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[Drawing a square root spiral] http://mathematica.stackexchange.com/questions/66969/drawing-a-square-root-spiral

Here is a start. I’m looking for a nice way to draw it.

Graphics[{EdgeForm[Black], White,
Polygon @ {{0, 0}, {-1, 0},
Sqrt[2] {Cos[#], Sin[#]} &amp;[Pi - (ArcCot[1])]},
Polygon @ {{0,  ...

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

[Weird behaviour for a vector InterpolatingFunction inside an NDSolve] http://mathematica.stackexchange.com/questions/105594/weird-behaviour-for-a-vector-interpolatingfunction-inside-an-ndsolve

I have run into some weird behaviour on the part of NDSolve which I ﬁnd pretty bizarre and which I would like to understand better.

Suppose, for the sake of argument, that I want to study the ODE ...

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[NDeigensystem returns error due to mesh discretization when calculating vibrations of a cantilever] http://mathematica.stackexchange.com/questions/105840/ndeigensystem-returns-error-due-to-mesh-discretization-when-calculating-vibratio

There was an transcription error in the code I provided in a previous post:

NDeigensystem returns complex non-hermitian error for the calculation of vibrations of a cantilever

This resulted in it ...

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[WhenEvent and Resetting of Variable in PDE when operation succeeds] http://mathematica.stackexchange.com/questions/105781/whenevent-and-resetting-of-variable-in-pde-when-operation-succeeds

I have had success in using WhenEvent to reset or change a variable within NDSolve with ordinary diﬀerential equations. My working, functioning MWE is:

Clear[usol, u, t, x, \[Lambda]]
usol = NDSolveValue[
...

### 5.48 Tuesday, February 2, 2016

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

[Exponential ﬁtting - isn’t actually a BUG there?] http://mathematica.stackexchange.com/questions/105002/exponential-fitting-isnt-actually-a-bug-there

There are many questions on this site about wrong exponential ﬁtting in Mathematica but no one considers this well-known problem as a potential bug. Usually people suggest well-known workarounds ...

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[Detecting components in timeseries] http://mathematica.stackexchange.com/questions/104950/detecting-components-in-timeseries

I’m looking at this sequence of values:

I’d like to detect the points where the center of the time-series shifts (around x=1000 and x=2000). Many of the transforms and smoothing methods I have ...

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[Generating Tuples with restrictions] http://mathematica.stackexchange.com/questions/105139/generating-tuples-with-restrictions

I am interested in a certain subset of all tuples. Generating all with Tuples and then ﬁltering is wasteful, and will ”blow up” very quickly.

For a concrete example, let’s say I want to ﬁnd all ...

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[Grid cuts my images] http://mathematica.stackexchange.com/questions/105061/grid-cuts-my-images

Bug introduced in V9.0 or earlier

and persisting through V10.3.1 or later

pic2 = ImageResize[
ImageCrop@Rasterize@Graphics@Disk[],
{Automatic, 40}]

Grid[{{pic2}}]

This is just ...

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[Non Standard Eigenfunction Plots of the Laplacian Over the Unit Square] http://mathematica.stackexchange.com/questions/105264/non-standard-eigenfunction-plots-of-the-laplacian-over-the-unit-square

I have recently been plotting eigenfunctions of the laplacian over the unit square using the NDEigensystem command. However, I have noticed something in the plots which puzzles me.

Below is an image ...

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[How to count the number of the tube] http://mathematica.stackexchange.com/questions/105229/how-to-count-the-number-of-the-tube

There is a picture Get the binary image

binimg = ColorSeparate[img][[2]] // Binarize[#, 0.25] &amp; // Thinning

Visulize the result of regconization

lines = ImageLines[binimg, 0.074];
...

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[Detecting X or O in a small image] http://mathematica.stackexchange.com/questions/105327/detecting-x-or-o-in-a-small-image

I am making a robot that plays Tic Tac Toe

Currently, I have code that will parse the board and separate it into an array of 9 images, each space on the board. How can I detect if the image ...

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

I’m aware that I can use (* ... *) to comment out stuﬀ in a notebook. Many languages have a syntax for single-line comments, such as

// in C, C++, Java, C#, ...
# in shell, Python, ...

For ...

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I use Mathematica mainly as an aid in symbolic attacks on problems, usually intermediate or harder and often number theoretic. While Reduce, Simplify, et al. are remarkably powerful, they of course ...

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

[What are the time and space complexities of Classify/Predict?] http://mathematica.stackexchange.com/questions/105366/what-are-the-time-and-space-complexities-of-classify-predict

Does anyone have knowledge of the O(n) time and space complexities for various model types supported by Classify[] and Predict[] during training and evaluation?

Here are a list of supported model ...

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[Finding eigenvalues in Mathematica: why so slow?] http://mathematica.stackexchange.com/questions/105224/finding-eigenvalues-in-mathematica-why-so-slow

I am trying to ﬁnd the eigensystem of a large sparse real symmetric matrix, and I only need the lowest 40 or so eigenstates. The relevant code is as follows:

TheModel[V0_, V1_, V2_, index_,  ...

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[Notebook created in cloud has odd errors in Mathematica 10.3.1] http://mathematica.stackexchange.com/questions/105019/notebook-created-in-cloud-has-odd-errors-in-mathematica-10-3-1

I’ve downloaded a notebook from develop.wolframcloud.com and opened it in 10.3.1 (running on Win 10). When I evaluate some cells I get syntax errors along the lines of...

Syntax::sntxf: "\"Clear[\"  ...

### 5.49 Tuesday, January 26, 2016

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

[List of Mathematica related acronyms and their real meaning] http://mathematica.stackexchange.com/questions/104593/list-of-mathematica-related-acronyms-and-their-real-meaning

A few years ago, Wolfram Inc. not only started to rename things around Mathematica, a lot of new technologies and frameworks were introduced as well. Now, we are left with a lot of acronyms and ...

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[What would you ask Mathematica to do on a big system?] http://mathematica.stackexchange.com/questions/104842/what-would-you-ask-mathematica-to-do-on-a-big-system

Our hardware supplier has given us the opportunity to test Mathematica on a big Windows system. The specs will be 1 to 4 TB of working memory and 12 sockets with 18 cores each. I got 1 full week of ...

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[What algorithm do the Compress and Uncompress functions use?] http://mathematica.stackexchange.com/questions/104660/what-algorithm-do-the-compress-and-uncompress-functions-use

Compress and Uncompress are used internally by Mathematica to compress things like 3D data in notebook ﬁles - data that I’d like to read independently. Does anyone have any idea if the compression ...

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[Is there any predictor-corrector method in Mathematica for solving nonlinear system of algebraic equations?] http://mathematica.stackexchange.com/questions/104578/is-there-any-predictor-corrector-method-in-mathematica-for-solving-nonlinear-sys

The FindRoot Function in Matheatica can easily be used to solve systems of nonlinear algebraic equations. But, I want to solve a system of nonlinear equations with variations of some parameters.

...

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[How do I deﬁne a periodic region?] http://mathematica.stackexchange.com/questions/104723/how-do-i-define-a-periodic-region

I’m trying to create a region of ”thick” grid-lines, like so

GRID = ImplicitRegion[((0 &lt;= x &lt;= 1 || 2 &lt;= x &lt;= 3 || 4 &lt;= x &lt;= 5 || 6 &lt;= x &lt;= 7 ||
8 &lt;= x &lt;= 9) || (0  ...

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[Zoom in on a 2D graph] http://mathematica.stackexchange.com/questions/104718/zoom-in-on-a-2d-graph

I have seen many queries on zooming in on plots etc. But I haven’t seen any regarding 2D graphs. For eg if I have a graph like

Graph[{1-&gt;2, 2-&gt;3, 3-&gt;1}].

It will create a graph. I have a ...

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[Fitting a curve to an image object: not a superellipse, not an egg curve.. what else?] http://mathematica.stackexchange.com/questions/104419/fitting-a-curve-to-an-image-object-not-a-superellipse-not-an-egg-curve-what

I’m facing the problem of quantifying the morphology of objects with such a shape (nannoconids...

they are fossils).

One of the ﬁnal goals is to produce a solid of revolution and compute ...

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

[Drawing a square root spiral] http://mathematica.stackexchange.com/questions/66969/drawing-a-square-root-spiral

Here is a start. I’m looking for a nice way to draw it.

Graphics[{EdgeForm[Black], White,
Polygon @ {{0, 0}, {-1, 0},
Sqrt[2] {Cos[#], Sin[#]} &amp;[Pi - (ArcCot[1])]},
Polygon @ {{0,  ...

—————————-

I use Mathematica mainly as an aid in symbolic attacks on problems, usually intermediate or harder and often number theoretic. While Reduce, Simplify, et al. are remarkably powerful, they of course ...

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

[Way to make contour labels on SliceContourPlot3D?] http://mathematica.stackexchange.com/questions/104590/way-to-make-contour-labels-on-slicecontourplot3d

SliceContourPlot3D doesn’t seem to come with the option of putting contour labels on the plots as far as I can see. I’m using the XStackedPlanes option. I don’t see any information about how one might ...

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[Implementation of a matrix formula] http://mathematica.stackexchange.com/questions/104463/implementation-of-a-matrix-formula

For the Bezier surface, which owns the following matrix deﬁnition:

where, $$B_{n,i}$$ denotes Bernstein-basis.

vec1 = {B[0],...,B[m]};
mat = {{P[0,0],...P[0,n]},...,{P[m,0],...P[m,n]}};
vec2=  ...

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[Can one preserve the appearance of the HorizontalGauge?] http://mathematica.stackexchange.com/questions/104524/can-one-preserve-the-appearance-of-the-horizontalgauge

I use sometimes the HorizontalGauge instead of a slider in Manipulateor instead of the ProgressIndicator. I ﬁnd it very convenient, since it gives quantitative information on the status of the ...

### 5.50 Tuesday, January 19, 2016

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

[Partition a list based on speciﬁc elements? Grab the sublists beginning with a certain marker elements] http://mathematica.stackexchange.com/questions/104153/partition-a-list-based-on-specific-elements-grab-the-sublists-beginning-with-a

Say I have the list

{{a}, {0, 2, 5}, {5, 4, 1}, {a}, {1, 1, 0}, {1, 4, 2},
{3, 3, 0}, {a}, {3, 2, 0}, {1, 4, 1}}

I would like to make sublists of everything beginning with the a element till ...

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[Why does Outer sometimes return a packed array, and sometimes not?] http://mathematica.stackexchange.com/questions/104040/why-does-outer-sometimes-return-a-packed-array-and-sometimes-not

For example

In[342]:=
test3 = Flatten[Outer[Plus, Range[1000], Range[1000]],
1]; // AbsoluteTiming

Out[342]= {0.0198735, Null}

returns PackedArray (examined by Developer‘PackedArrayQ[test3] ...

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[Interpolation function way oﬀ] http://mathematica.stackexchange.com/questions/104037/interpolation-function-way-off

I have a simple list of data points to which I would like to ﬁt an interpolation function. However, the results given by Interpolation[] gives an oscillating function which is not warranted by the ...

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[How to deal with bad arguments when a function’s UpValues is a pure-function?] http://mathematica.stackexchange.com/questions/103952/how-to-deal-with-bad-arguments-when-a-functions-upvalues-is-a-pure-function

In practice, I needs to deﬁne the UpValues of a user-deﬁned function. For instance, the operation of function like diﬀerential formula , expansion and so on.

Here, I will give a example that came ...

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[Using Solve to solve the equation $$x^{1/3}=-1$$] http://mathematica.stackexchange.com/questions/104281/using-solve-to-solve-the-equation-x1-3-1

I am curious why this command returned no answers:

Solve[x^(1/3) == -1, x]

Gives this output:

(* {} *)

I was able to get around the problem with this:

Solve[Surd[x, 3] == -1, x]

Which  ...


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[How do you convert RGBColor to an HTML-style string?] http://mathematica.stackexchange.com/questions/103999/how-do-you-convert-rgbcolor-to-an-html-style-string

If I run some color processing function, like:

Blend[RGBColor /@ {"#DC4E00", "#000000", "#822250", "#FCC11B"}]

I get back a RGBColor object:

RGBColor[0.5901960784313726, 0.29901960784313725,  ...

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[ReplaceAll behavior change from 10.2 to 10.3] http://mathematica.stackexchange.com/questions/104354/replaceall-behavior-change-from-10-2-to-10-3

Executing:

replace[res_] := res /. {a_Integer, b_Integer} :&gt; (a + b);
l1 = &lt;|"respID" -&gt; {1,2} , "key2" -&gt; &lt;|"key2" -&gt; {2, 1}|&gt;|&gt;;
l2 = {"respID" -&gt; {1,2} , "key2" -&gt;  ...

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

[Drawing a square root spiral] http://mathematica.stackexchange.com/questions/66969/drawing-a-square-root-spiral

Here is a start. I’m looking for a nice way to draw it.

Graphics[{EdgeForm[Black], White,
Polygon @ {{0, 0}, {-1, 0},
Sqrt[2] {Cos[#], Sin[#]} &amp;[Pi - (ArcCot[1])]},
Polygon @ {{0,  ...

—————————-

[Mathematica 10.0.x freezes in Initializing kernels] http://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 ...

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

[How to ﬁnd and show a point value on the line?] http://mathematica.stackexchange.com/questions/104384/how-to-find-and-show-a-point-value-on-the-line

Manipulate[
Module[{eqns, f},

eqns = {y'[x] ==
aa3*y[x]^3 + aa2*y[x]^2 + aa1*y[x] + aa0[t] + bb[t]/y[x],
y[0] == 15};

f = NDSolve[eqns, y, {x, 0, 1}][[1, 1, -1]];

Plot[f[x], {x, 0,  ...

- asked by user37037 (1 vote)

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[Is it possible for librarylink function to be Listable like that in Compile?] http://mathematica.stackexchange.com/questions/104382/is-it-possible-for-librarylink-function-to-be-listable-like-that-in-compile

We know in Compile, there is an Option RuntimeAttributes ; Listable which can let the compiled function easily explore the power of thread parallelization.

So is it possible for a librarylink ...

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[How could get all escape characters in Mathematica?] http://mathematica.stackexchange.com/questions/104299/how-could-get-all-escape-characters-in-mathematica

I am evaluating expression by using KernelLink.

But the kernel will be suspended endless when meets a invalid escape character. a\abc, \[badEscape] for example.

So I have to ﬁlter all the invalid ...

### 5.51 Tuesday, January 12, 2016

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

[Why is SatisﬁabilityCount faster than SatisﬁableQ?] http://mathematica.stackexchange.com/questions/103726/why-is-satisfiabilitycount-faster-than-satisfiableq

Consider the following (large) Boolean expression, which arose in a SAT problem. (The expression is not satisﬁable.)

bigExpr = Import["http://pastebin.com/raw/gEgGQ26S"];

On my system (Mathematica ...

—————————-

I have just noticed that

x /. &lt;|x -&gt; 123|&gt;

evaluates to

123

In other words, the association seems to behave as a rule. I didn’t see any example or reference to this behavior in the ...

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[Is it possible to Parallelize Select?] http://mathematica.stackexchange.com/questions/103548/is-it-possible-to-parallelize-select

Given a large list of elements, is it possible to improve Select by parallelizing?

An example: from a 10,000,000-element list of integers between 1 and 10, select all primes

rl = RandomInteger[10, ...

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[how to enforce a symmetric solution with fem?] http://mathematica.stackexchange.com/questions/103606/how-to-enforce-a-symmetric-solution-with-fem

I’m solving the laplace equation in a domain with holes, and I need to compute the integral of the gradient on the boundary of these holes.

For that I deﬁne a mesh and solve the laplace equation ...

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[Best way to emulate MATLAB’s bsxfun using Map and similar functions] http://mathematica.stackexchange.com/questions/103527/best-way-to-emulate-matlabs-bsxfun-using-map-and-similar-functions

Given a matrix, we want to subtract the mean of each column, from all entries in that column. So given this matrix:

(mat = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12) // MatrixForm

the mean ...

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[Order of evaluation - does Mathematica evaluate variables before or after substitution?] http://mathematica.stackexchange.com/questions/103800/order-of-evaluation-does-mathematica-evaluate-variables-before-or-after-substi

Let’s say I write

y = x^2;
x = 10;
z = y + y^2 + y^3

Does Mathematica internally evaluate y before or after substituting it into z? I.e., does Mathematica internally evaluate this as

y = x^2 =  ...

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[How to ”inform” successive ContourPlot calculations?] http://mathematica.stackexchange.com/questions/103673/how-to-inform-successive-contourplot-calculations

I need to draw some contour plots of very non-linear functions. As a simple example, take a Mandelbrot Set divergence contour near $$z\approx i$$. (Just to be clear, I’m not trying to write a ...

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

[How to calculate contour integrals with Mathematica?] http://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?

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[How do I remove grid from this photo?] http://mathematica.stackexchange.com/questions/88494/how-do-i-remove-grid-from-this-photo

I found this cat a month ago, and I’m not his owners’ friend so the mosquito grid was the inevitable problem. I would like to post-process this photo to get rid of it, but I don’t know exactly how ...

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

[Fitting data with unique variable per measurement] http://mathematica.stackexchange.com/questions/103770/fitting-data-with-unique-variable-per-measurement

Imagine we are in the following situation, we have a nonlinear system of functions $$f$$ with coordinates $$x_i$$, and unknown parameters $$\delta _i$$’s and $$t$$. Let this system be deﬁned as,

...

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[‘ParallelTable‘ pending the MathKernel after execution] http://mathematica.stackexchange.com/questions/103611/paralleltable-pending-the-mathkernel-after-execution

I have done a ParallelTable computation in script mode. After execution, the output is ﬁne and I’ve got all the data I needed. but the kernel seems pending, usually it should exit after they ﬁnished ...

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[Call Magma in Mathematica] http://mathematica.stackexchange.com/questions/103602/call-magma-in-mathematica

I’ve written some code in Mathematica, related to some group theory questions I have. Subsequently, I found that part of the code could be signiﬁcantly sped up if I could just call a routine in ...

### 5.52 Tuesday, January 5, 2016

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

[Optional throws error when called from a package. Workaround?] http://mathematica.stackexchange.com/questions/103084/optional-throws-error-when-called-from-a-package-workaround

Bug introduced in 8.0 or earlier and persisting through 10.3 or later.

Case number: 305932.

In the front-end notebook (Mathematica 9.0 and 10.2):

g[x: Optional[_,default]]:=x;

has no problems, ...

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[How to automatically have ContourLabels in middle of Contour lines if speciﬁc levels are not speciﬁed?] http://mathematica.stackexchange.com/questions/103289/how-to-automatically-have-contourlabels-in-middle-of-contour-lines-if-specific-l

I looked at all the questions/answers relating to placement of ContourLabels but could not ﬁnd an answer to this. Some of the answers before are based on user giving before-hand, the Contours levels ...

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[Generating assignments and transforming code inside Holding forms when generating code] http://mathematica.stackexchange.com/questions/103263/generating-assignments-and-transforming-code-inside-holding-forms-when-generatin

I have been playing with slightly above trivial code manipulations in Mathematica. I thought Mathematica would be great for this kind of work because of rule replacement and expression manipulation, ...

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[Overlay vs Show for plots?] http://mathematica.stackexchange.com/questions/103073/overlay-vs-show-for-plots

I am trying to understand the diﬀerences of Overlay and Show to combine two plots. A typical use case is to superpose a ListPlot of some data with a Plot of a curve to ﬁt the data.

The following ...

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[What should I learn from DSolve working better with a named constant than a number in this case?] http://mathematica.stackexchange.com/questions/103327/what-should-i-learn-from-dsolve-working-better-with-a-named-constant-than-a-numb

I have an equation

Here $$b$$ and $$r$$ are lengths, and $$\phi$$ is an angle (in radians, so ...

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[W—A or Mathematica for CountryData?] http://mathematica.stackexchange.com/questions/103302/wa-or-mathematica-for-countrydata

Sometimes W—A gives you something ...

WolframAlpha["electricity production of the United States in 2007", "Result"]

... not available in the WDF

CountryData["UnitedStates",  ...

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[How to implement JoinTo eﬃciently?] http://mathematica.stackexchange.com/questions/103238/how-to-implement-jointo-efficiently

AppendTo is not eﬃcient so I’m not quite sure of the best way to implement its analogue for joining (e.g. in python this would be extend function). So how can this be improved:

ClearAll[JoinTo]; ...

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

[Find eigen energies of time-independent Schrodinger equation] http://mathematica.stackexchange.com/questions/32293/find-eigen-energies-of-time-independent-schrodinger-equation

I’m trying to get the eigenvalues of a one dimensional time-independent Schrodinger equation,

$$-\frac {h^2}{2m_0}\frac {d^2\psi }{dx^2}+U(x)~\psi =Ei~\psi$$

where U(x) is some potential and Ei is the ...

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[How to create word clouds?] http://mathematica.stackexchange.com/questions/2334/how-to-create-word-clouds

Word clouds are rather useless fancy and visually appealing plots, where words are plotted with diﬀerent sizes according to their frequency in a corpus. Many applications exist out there (Wordle, ...

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

[How can I import from a usb webcam on the raspberry pi?] http://mathematica.stackexchange.com/questions/103364/how-can-i-import-from-a-usb-webcam-on-the-raspberry-pi

I’m trying to set up a raspberry pi as a webcam server and I need to import images into a mathematica notebook on the raspberry pi. I tried using CurrentImage[] just to test it but I got an error just ...

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[How to change default font for all existing notebooks at once?] http://mathematica.stackexchange.com/questions/103053/how-to-change-default-font-for-all-existing-notebooks-at-once

By default, Mathematica 9 and 10 use Gill Sans MT fonts for headings of title/subtitle/section/subsection/subsubsection. Unfortunately, Gill Sans MT fonts have no Cyrillic letters, so that all ...

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[VERY slow to solve a nonlinear equation involving matrix eigenvalues] http://mathematica.stackexchange.com/questions/103282/very-slow-to-solve-a-nonlinear-equation-involving-matrix-eigenvalues

I am trying to solve a problem similar to the following:

f[k_, a_] := (
Matrix = {{0.05, (a*k)^2}, {(a*k)^2, -0.05}};

{eps, psi} = Eigensystem[Matrix];

{eps,psi} = {eps[[#]], psi[[#]]} &amp;@
...