Create matrix with randomly distributed integers, with exact relative abundances

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Christopher
Christopher 2014-10-14
评论： Thorsten 2014-10-14
I want to create a matrix of randomly distributed integers between 0 and 4 (0, 1, 2, 3, or 4). However, I want the abundance of each integer to conform to a predetermined value.
So if I have a vector of abundances (e.g.):
% 0 1 2 3 4 <--corresponding random numbers
mo = [0 0.5533 0.1346 0.1167 0.1954]; % abundance of random
numbers
and I want to fill up a matrix:
P = zeros(100,100);
I can see that the abundances should be
abund = round(mo.*size(P,1).*size(P,2));
= 0 5533 1346 1167 1954
But how do I fill up the matrix P with these randomly distributed numbers? The important thing is that the abundances are exactly as predetermined.

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回答（1 个）

Thorsten
Thorsten 2014-10-14
编辑：Thorsten 2014-10-14
values = [0:4];
mo = [0 0.5533 0.1346 0.1167 0.1954];
a = 100; b = 100;
% create a vector where each value appears mo(i)*a*b times
P = [];
for i = 1:numel(mo)
P = [P values(i)*ones(1, round(a*b*mo(i)))];
end
% randomize and reshape
P = P(randperm(a*b));
P = reshape(P, [a b]);
% check
hi = hist(P(:), [0:4])
  2 个评论
Christopher
Christopher 2014-10-14
编辑：Christopher 2014-10-14
almost correct, but the algorithm fails if i set a=120 and b=120. The array becomes 14399 elements instead of the correct 14400, so reshape fails. Can this be fixed easily?
Edit: sorry the problem is that my vector 'mo' has more decimal places. Is there a way to ensure that the correct size vector for P results (a*b) for any real numbers in the vector 'mo' (as long as mo sums to 1)?

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