Creating random integer row array each element different upper limit and sum of elements add up to a number
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I am looking for a intutuve code to generate 1x6 array where each element is random integer (with in specific upper limit) and sums to a given number.
For example a random array where element lower limit [ 0 0 0 0 0 0] and upper limit [ 9 12 25 6 14 7]. The sum of the random integer number adds up to 24, e.g.
[4 3 8 1 3 4 1]
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Ameer Hamza
2020-9-24
编辑：Ameer Hamza
2020-9-28
See this excellent FEX package by John: https://www.mathworks.com/matlabcentral/fileexchange/49795-randfixedlinearcombination. However, It generates fractional numbers. Following code proposes one modification. I don't know how it will change the probability distribution.
lb = [0 0 0 0 0 0];
ub = [9 12 25 6 14 7];
n = numel(lb);
s = 24;
x = round(randFixedLinearCombination(1, s, [1 1 1 1 1 1], lb, ub));
k = sum(x) - s;
if k > 0
idx = find(x >= (lb+1));
idx = idx(randperm(numel(idx), k));
x(idx) = x(idx) - 1;
else
idx = find(x <= (ub-1));
idx = idx(randperm(numel(idx), -k));
x(idx) = x(idx) + 1;
end
8 个评论
Biswanath Mahanty
2020-9-27
Bruno Luong
2020-9-27
I believe it must have a minus in the second if-branch
idx = randperm(n, -k)
John D'Errico
2020-9-27
You download randFixedLinearCombination from the File Exchange. It is part of MATLAB, in the sense that you need do nothing more than download it. NO cost. Ameer gave you the link.
Ameer Hamza
2020-9-27
John: Thanks for the comment.
Bruno: Thanks for pointing out. You are correct. It should be -k.
Biswanath: As John mentioned, download this package from the link and place it in MATLAB's path: https://www.mathworks.com/help/matlab/matlab_env/add-remove-or-reorder-folders-on-the-search-path.html
Bruno Luong
2020-9-27
编辑：Bruno Luong
2020-9-27
The rounding method is still flawed. The results might get out of bound once they are added by +/-1. You have to select the subset more careful than randperm.
Ameer Hamza
2020-9-27
Yes, thanks for pointing out the issue. I have updated the code. I am not sure if there still are some cases where it will fail to meet the constraint.
Bruno Luong
2020-9-27
编辑：Bruno Luong
2020-9-27
I think you can do better if you replace the first filtering with <= >= tests rather than strict inequality.
It still not perfect though.
Ameer Hamza
2020-9-28
Yes, I guess this will fail when the bounds are very tight in accordance with the sum constraints. The point about inequality is also valid. For the given bounds, the method does not seem to fail.
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