Creating random integer row array each element different upper limit and sum of elements add up to a number
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Biswanath Mahanty
on 24 Sep 2020
Edited: Ameer Hamza
on 28 Sep 2020
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
on 24 Sep 2020
Edited: Ameer Hamza
on 28 Sep 2020
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 Comments
Bruno Luong
on 27 Sep 2020
Edited: Bruno Luong
on 27 Sep 2020
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
on 28 Sep 2020
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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