================================== Top new questions this week: ==================================
[Finding \(n^{\text {th}}\) largest/smallest element] https://mathematica.stackexchange.com/questions/154944/finding-n-textth-largest-smallest-element
Ordering can quickly find the position of the largest/smallest element in a list, but finding the position of the \(n^{\text {th}}\) largest/smallest element is much slower:
data = RandomReal[10, 10^7];
...
- asked by Carl Woll (13 votes), answered by Carl Woll (12 votes)
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[Fast pairwise SameQ test of an ordered list] https://mathematica.stackexchange.com/questions/155017/fast-pairwise-sameq-test-of-an-ordered-list
I have an ordered list of \(N\) numbers, and I want to find out whether adjacent numbers are SameQ or not, returning a list of 0s and 1s of length \(N-1\). One approach is something like:
...
- asked by Carl Woll (11 votes), answered by jkuczm (8 votes)
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[Given an ordered set S, find the points in S corresponding to another list] https://mathematica.stackexchange.com/questions/154893/given-an-ordered-set-s-find-the-points-in-s-corresponding-to-another-list
Given a sorted list of numbers \(S\), I want to create a function that accepts a list of numbers \(L\) and for each number \(l \in L\) it returns the index of the largest number \(s \in S\) such that ...
- asked by Carl Woll (11 votes), answered by nikie (13 votes)
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[Geolocate multiple IP addresses] https://mathematica.stackexchange.com/questions/155076/geolocate-multiple-ip-addresses
I would like to geolocate a few hundred IP addresses (as part of analysing server logs). What is the best way to do this using Mathematica?
Does Mathematica have any builtin functionality for this?
...
- asked by Szabolcs (9 votes), answered by Szabolcs (9 votes)
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[How to connect two images] https://mathematica.stackexchange.com/questions/155093/how-to-connect-two-images
I have talk about how to catenate two images whose have same part totally in my this post.
But in this case two images have similar information, not totally same.
img1 = Import @ ...
- asked by yode (9 votes), answered by Kuba (8 votes)
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[Filter elements in descending order] https://mathematica.stackexchange.com/questions/154761/filter-elements-in-descending-order
I want to solve the following problem efficiently:
Given a list of pairs (value, data), I want to remove all the pairs so that the resulting list has the value property of its elements sorted. That ...
- asked by José D. (9 votes), answered by Mathe172 (9 votes)
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[Changing numbers inside list to a list] https://mathematica.stackexchange.com/questions/154911/changing-numbers-inside-list-to-a-list
I have a list wich contains numbers and other lists, and what I want is to change every number x to x,0.
So if the function I’m seeking is called f, then
a = {1,Pi,2+3I,{1,2},{3,4},-2} f[a] ...
- asked by Garmekain (8 votes), answered by John Joseph M. Carrasco (10 votes)
================================== Greatest hits from previous weeks: ==================================
[Is it possible to draw this figure using Mathematica?] https://mathematica.stackexchange.com/questions/110848/is-it-possible-to-draw-this-figure-using-mathematica
The figure is
See the how-to video or a speeded-up GIF.
I believe it should be possible to draw this figure programmatically using some Random function, but I’m rather new to Mathematica, so I ...
- asked by AccidentalFourierTransform (62 votes), answered by M.R. (86 votes)
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[Can Mathematica do symbolic linear algebra?] https://mathematica.stackexchange.com/questions/3242/can-mathematica-do-symbolic-linear-algebra
For instance, is there some way I can say "let A and B be arbitrary real \(m\times n\) and \(k\times m\) matrices, Simplify[Transpose[Transpose[A].Transpose[B]]]" and Mathematica would simplify it to B.A? ...
- asked by nikie (47 votes), answered by helen (25 votes)
================================== Can you answer these? ==================================
[Strange result for an improper integral \(\int _{0}^{1}\frac {x^{-1/2}}{e^{x}-1} \sin \left (\frac {1}{x}\right )dx\)] https://mathematica.stackexchange.com/questions/155066/strange-result-for-an-improper-integral-int-01-fracx-1-2ex-1-s
The improper integral \[\int _{0}^{1}\frac {x^{-1/2}}{e^{x}-1} \sin \left (\frac {1}{x}\right )dx\] is convergent conditionally.
(Applying Dirichlet Test, \[\frac {x^{-1/2}}{e^{x}-1}\] ...
- asked by user250236 (1 vote)
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[Perplexing simplification of RotationMatrix] https://mathematica.stackexchange.com/questions/154793/perplexing-simplification-of-rotationmatrix
The result of
FullSimplify[RotationMatrix[, {Cos[], Sin[], 0}], > 0].{0, 0, 1}
in Mathematica 11 is
{Sign[Sec[]]^2 Sin[] Sin[], -Cos[] Sin[], Cos[]}
instead of the nicer result ...
- asked by theindigamer (1 vote)
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[collecting terms with different order] https://mathematica.stackexchange.com/questions/154849/collecting-terms-with-different-order
I am using homotopy perturbation method to solve nonlinear ODE.
The first step is to introduce P parameter and collect different order of P.
The code is like this:
Collect[(1 - p) ((((1 + ...
- asked by sajad.sharhani (1 vote)