MATLAB: How to generate specific number of specific integers within a range

randirandom number generator

I want to generate a random array of 8 integers within [1,4] where each integer appears exactly twice. Examples:
1 1 2 2 3 3 4 4
4 2 1 2 3 1 3 4
2 4 1 2 3 4 3 1
I know randi(4,8,1) gives a random array of 8 integers within [1,4] but it does not specify how many come from which integer. Is there a built in matlab function that does this? If not, what should I do?

Best Answer

This is easy with randperm:
>> vec = repmat(1:4,1,2);
>> out = vec(randperm(numel(vec)))
out =
   2   3   2   4   1   1   4   3
>> out = vec(randperm(numel(vec)))
out =
   1   4   2   3   2   1   3   4
>> out = vec(randperm(numel(vec)))
out =
   2   1   2   4   3   3   4   1
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