Mathematica Stack Exchange Community Digest

Top new questions this week:

Possible bug involving derivative of BesselI

In Mathematica 12.0, I run the following code: f[x_] = BesselI[0, x]; f'[x] which returns BesselI[1, x] as expected. But if I enter f[x_] = BesselI[0, 1.0 x]; f'[x] I get 0.5 (BesselI[1, 1. x] ...

calculus-and-analysis bugs special-functions  
asked by Alex S 7 votes
answered by Michael E2 3 votes

Can Wolfram Language enforce pure functions?

Is there a feature in Wolfram Language that supports or enforces pure functions? WL has something that it calls "pure functions" in its documentation, but these are most emphatically not pure ...

pure-function  
asked by orome 7 votes

Effectively gather data with small differences

I frequently encounter themes where I have a set of data, then I need to gather up those identical ones. However, due to numerical error in data, GatherBy cannot be directly implemented, while Gather ...

list-manipulation performance-tuning gathering  
asked by Wjx 6 votes
answered by Roman 9 votes

Merge list repeating elements

Suppose I have a list with mixed elements {{{a,b},{c,d}},{{e,f},{h,i}}} Is there a way so that I can reshuffle the elements to get the following? ...

list-manipulation table combinatorics partitions  
asked by Alessandro Mininno 6 votes
answered by kglr 8 votes

Removing duplicate rows and appending from a table of lists

For the table x with three lists per row: x={{{10, 56, 528, 6240, 97920, 1751040, 38154240, 1058365440, 31677972480, 1134275788800, 45248407142400}, {2, 14, 15, 1, 2}, {1}}, {{3, 60, 280, ...

list-manipulation table  
asked by Jamie M 6 votes
answered by kglr 8 votes

All possible combinations of ways to write an equation

I want to define a function in Mathematica where I get all combinations of an expression, e.g., input: {q,p1,p2} Output: {q + p1 + p2, q + p1 - p2, q - p1 + p2, -q + p1 + p2, -q - p1 + p2, -q + p1 ...

list-manipulation combinatorics  
asked by NeAr 6 votes
answered by Fraccalo 12 votes

AtomQ[Counts[{a, c, d, b, a, c, b}]] gives True. Why?

I don’t understand this: In[]: AtomQ[Counts[{a, c, d, b, a, c, b}]] Out[]: True It looks like an expression. Does this have to do with the realization of the expression? Dani

core-language  
asked by Dani 6 votes
answered by WReach 12 votes

Greatest hits from previous weeks:

Is there a syntax for single-line comments for notebooks?

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 ...

syntax comment  
asked by Peeter Joot 61 votes
answered by Szabolcs 62 votes

How can I improve Mathematica's resolution on a macbook retina display?

Mathematica 9.0 looks a bit fuzzy on the retina screen, how can I increase the resolution? Here another screenshot showing a direct comparison between the browser and Mathematica

front-end version-9 mac-os-x  
asked by Tom Wellington 43 votes
answered by canadian_historian 20 votes

Extract real part of a complex expression better than Re does

I have a complex expression with real positive variables only. Mathematica Input Style: PP = -((α (γ Cosh[y1 α] + α Sinh[y1 α])(-γ Cosh[(-L + y2) α] + α Sinh[(-L + y2) α])) /(s (2 α γ Cosh[L α] ...

symbolic trigonometry  
asked by max 31 votes
answered by nixeagle 49 votes

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, #>7&] gives the elements themselves, and Position[x,8] gives the ...

list-manipulation  
asked by PeterR 61 votes
answered by J. M. is in limbo 59 votes

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 ...

bugs front-end system kernel-startup paclets  
asked by mitcheljh 78 votes
answered by ilian 99 votes

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 ...

image-processing image fourier-analysis  
asked by user8727 13 votes
answered by Nasser 32 votes

Plotting the frequency spectrum of a data series using Fourier

testData = Table[N@Sin[500 x], {x, 0, 100}]; ListLinePlot[Abs[Fourier[testData]], PlotRange -> Full] Gives me Which I do not expect because the Fourier Transform is FourierTransform[Sin[500 ...

fourier-analysis  
asked by C. E. 14 votes
answered by KennyColnago 16 votes

Can you answer these questions?

Alter maximum output size from Linux command line

I recently installed Wolfram Mathematica in a instance in Google Cloud using GPUs and I'm running it inside Jupyter Notebook, Python 3, using Wolfram Client library. However, big outputs, like a ...

wolfram-cloud webmathematica mathematica-online  
asked by Rubens_Zimbres 1 vote

Share package functions without sharing context

I'm trying to find a solution to a problem that I've been struggling with for a while. I asked a variant of the question here: Automatically load init.m without sharing CellContext, but think I've ...

packages contexts  
asked by KHAAAAAAAAN 2 votes

Numerically solving an algebraic equation

I have asked a similar question earlier, but I am still stuck at the same problem. I would like to solve an algebraic equation of the form Tan[d*Sqrt[-k^2 + w^2*(1 + (1 - w^2)^(-1))]] == Sqrt[k^2 - ...

equation-solving numerical-value  
asked by xabdax 1 vote
answered by MikeY 0 votes
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