MATLAB: How to divide a vector randomly in 3 groups

dividegroupsMATLABrandomrandomlyvector

Hello everyone,
I have the following problem: I have a column vector A = [1:1000]' and I would like to divide it in 3 groups randomly. (For example in A1=[1:200], A2=[1:450], A3=[1:350]) It doesn't matter if the groups are contiguous. That is, if the first group is made up of sample 1 to 200, the second group should be made up of sample 201 to 650, etc.
The only requirement is that each group must contain at least 10% to 80% of the data. That is, there cannot be a group with 2 samples and the rest with 499 and 499.
Thanks in advance,
J.F.

Best Answer

Based on my current understanding, maybe this rejection method might do what you want. Again, since there are only three groups the rejection percentage of about 23% might be tolerable to you.
A = your vector
n = numel(A);
n10 = floor(0.10*n);
while( true )
    p = n10 + sort(randperm(n-2*n10+1,2)-1);
    if( p(1) >= n10 && p(2)-p(1) >= n10 && n-p(2) >= n10 )
        break;
    end
end
G = {A(1:p(1)),A(p(1)+1:p(2)),A(p(2)+1:end)};
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