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Editorial Team
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Asked: 2026-06-03T08:20:01+00:00

Okay, this is like the 5th time I have had to ask this question,

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Okay, this is like the 5th time I have had to ask this question, and still nobody has been able to give me an answer or solution. But here we go again …

I want to run a very simple little MATLAB program. All it does is RANDOMLY display images from a directory. Here is my code:

files = dir(fullfile(matlabroot,'toolbox','semjudge',bpic,'*.png')); 
nFiles = numel(files);
combos = nchoosek(1:nFiles, 2);
index = combos(randperm(size(combos, 1)), :); 
picture1 = files(index(nRep,1)).name;
picture2 = files(index(nRep,2)).name;
image1 = fullfile(matlabroot,'toolbox','semjudge',bpic,picture1);
image2 = fullfile(matlabroot,'toolbox','semjudge',bpic,picture2);
subplot(1,2,1); imshow(image1); 
subplot(1,2,2); imshow(image2);

I have tried several different iterations of this, including replacing “nchoosek” with “randsample.”

But it doesn’t work! Every time I run the program, the script runs the same image files in the same order. Why is it doing this? It’s like it randomized the image files the first time I ran it, but now it only runs them in that order, instead of randomizing them every time the script is run.

Can somebody please help me with this?

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1 Answer

  1. Editorial Team

    The pseudo-random number generator starts off from a specific seed. The “random” numbers provided are deterministic. You need to change the seed to change these numbers.

    The benefit of this is that even if you use pseudo-randomness in your algorithm, you can always replay a run by using the same seed again.

    Reference: http://www.mathworks.de/help/techdoc/ref/rng.html

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