4.18 Tuesday, August 22, 2017

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

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

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

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

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

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

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

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

For learning purposes I created this code:

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

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

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

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

Background

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

can’t show everything but headers contain:

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

and body (returned from URLRead) contains ...

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

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

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

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

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

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

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

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

f[t_] :=  ...

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

- asked by Shredderroy (1 vote)

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

Intro

Consider these two equal expressions of the variance

\[\frac {\sum _{i=1}^n x(i)^2}{n}-\frac {\left (\sum _{i=1}^n x(i)\right ){}^2}{n^2}\]

and

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

- asked by Remi.b (1 vote)

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

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

n[x_] = PDF[NormalDistribution[, ], x]; 
2[x1_,  ...

- asked by Glostas (1 vote)