Mathematica Weekly Newsletter
Mathematica Weekly Newsletter

Top new questions this week:

How to sort digits in a string while keeping other characters untouched?

Now there is a string with digits and letters, for instance, "95uge678r3gi89hgfe30kgh063d51". And the expected output is "00uge133r3gi55hgfe66kgh788d99". I am able to do it in this way ...

list-manipulation string-manipulation code-review  
asked by Felix 12 votes
answered by Mr.Wizard 8 votes

Expansion of a hypergeometric function takes ages with Mathematica 9 and 10 (regression?)

Mathematica 8 (Linux version) can evaluate AbsoluteTiming[Series[Hypergeometric2F1[1, 1 - eps/2, 3 - eps, 1/2], {eps, 0, 0}]] in no time. On one of the university machines the result is {0.175840, ...

bugs series-expansion  
asked by vsht 10 votes
answered by Eric Towers 4 votes

Opposite of StringSplit

What is an appropriate command that does the opposite of the following. StringSplit["a b c d e f g"," "]

version-10 education  
asked by William 10 votes
answered by Pickett 16 votes

Why can I not replace a Dataset using a rule?

Simple replacement of a Dataset object does not seem to follow the expected behavior... Dataset[{}] /. _Dataset->1 Returns the empty Dataset not 1 as I would have expected. Whereas...

pattern-matching dataset  
asked by Ymareth 9 votes
answered by WReach 11 votes

Turning a set of random walk data 45 degrees

I have a set of data that is just a "random" (generated by me, not by computer) sequence of length 2000 of 1's and (-1)'s. I used it to plot a 1-D random walk where +1 is step up, (-1) is step down, ...

plotting list-manipulation data random  
asked by Solarmew 8 votes
answered by Karsten 7. 4 votes

Unexpected slowness checking for empty list?

I thought I had a firm understanding of the differences between Equal and SameQ, but this has me puzzled: test = RandomInteger[100000000, 10000000]; {} == test // AbsoluteTiming {} === test // ...

list-manipulation performance-tuning expression-test  
asked by rasher 8 votes
answered by Mr.Wizard 9 votes

Mathematica on Raspberry Pi

Can I develop BSD/MIT open-source library for Mathematica using free non-commercial version on Raspberry Pi? To state it differently: does the non-commercial limitation of Mathematica on RPi limit ...

raspberry-pi license open-source licensing  
asked by denfromufa 7 votes
answered by denfromufa 3 votes

Greatest hits from previous weeks:

How to create a new "person curve"?

Wolfram|Alpha has a whole collection┬╣ of parametric curves that create images of famous people. To see them, enter WolframAlpha["person curve"] into a Mathematica notebook, or person curve into ...

graphics image-processing algorithm wolfram-alpha-queries generative-art  
asked by Simon 49 votes
answered by Vitaliy Kaurov 21 votes

How to create effect like Van Gogh's stroke brush?

I need to apply Van Gogh's stroke brush effect to a random image Take the following image as an example: Thank you so much if you could help!

image-processing code-request generative-art  
asked by user10495 23 votes
answered by Simon Woods 33 votes

Can you answer these?

NDSolve Poisson PDE for rectangle with hole

When I solved the Poisson PDE with function NDSolve in a rectangular domain with hole in the center, and search the first derivative with x and y why appear these protrusions on the diagram around the ...

plotting differential-equations  
asked by wlkyr 1 vote

How to handle solution returned by ParametricNDSolveValue in FindRoot

i was trying to solve a problem relative to root finding in a system of differential equations; here's a simpler case. With two distinct set of parametric differential equations, i'm able to find the ...

equation-solving differential-equations  
asked by Ivactheseeker 2 votes

FindDivisions behavior changed?

I seem to recall using FindDivisions as a quick way to get all numbers in an interval that are divisible by a member of some set of integers, e.g. FindDivisions[{1,100,{2,3,5}}] gave me lists of ...

asked by rasher 4 votes
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