If you run a randperm on an array, then a second time on a second array of the same dimensions, will both be shuffled in the same way?

I have a program where a microscope image is shuffled using randperm, but I have images at two different wavelengths at the same time and want to shuffle both in the same way. If I use randperm on a, say, 300x400 image and then rerun the program on another 300x400 image, does randperm do the same operation and shuffle both in the same way, or does it change? If it does change, how might I be sure both were shuffled the same?

Answer 1

[Walter Roberson]

randperm uses the default random number generator. If you have set up the same random number generator seed and ask for the same number of output values then they will be the same. If you do not set up the same random seed then the outputs will seldom be the same.

randperm() does not shuffle images; randperm can be used to generate indices that can be used to shuffle images. You can record the generated order before shuffling the first image and use that recorded order to shuffle the second.

[Kavorka]

I'm very new to programming, any advice on how to record the order and apply it to both shuffles?

My randperm function looks like:

imgVector=imgVector(randperm(sqrelements));

sqrelements is number of array elements (at this point I've converted the array into a vector for other reasons)

This appears in two identical functions I run one after the other, once for each image (imgVector and imgVector2)

[Steven Lord]

 shuffledIndices = randperm(sqrelements);
 imgVector = imgVector(shuffledIndices);
 imgVector2 = imgVector2(shuffledIndices);

[Walter Roberson]

randorder = randperm(sqrelements);
imgVector=imgVector(randorder);
othervector = othervector(randorder);