How to make sure each column in a matrix sums exactly to 1?

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Marco
Marco 2015-8-7
评论： Marco 2015-8-7
Hello,
I would need to create a matrix of random numbers between 1 and 0, where the diagonal of the matrix is composed of zeros only and where each column sums to 1. I approximately reached the result by the following code, but some of the columns add up to slightly less than 1 (around 0.97). Why doesn't Matlab manage to normalize all of them to 1? Is there a way to solve the problem?
Here's the code:
a = [0:0.0001:1];
b(1:10000) = (0.5/10000);
F=randsrc(100,100,[a;0.5 b]);
columnSums = sum(F);
N=100;
for n=1:N
F(n,n)=0;
end
for i = 1:numel(columnSums)
F(:,i) = F(:,i)./columnSums(i);
end
Thank you! Marco

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采纳的回答

Lukas Bystricky
Lukas Bystricky 2015-8-7
It's because you're calculating the column sums and then setting the diagonal entries to 0. If you calculate the sums after you modify the diagonal then what you wrote would work.

更多回答（1 个）

Torsten
Torsten 2015-8-7
a = [0:0.0001:1];
b(1:10000) = (0.5/10000);
F=randsrc(100,100,[a;0.5 b]);
N=100;
for n=1:N
F(n,n)=0;
end
columnSums = sum(F);
for i = 1:numel(columnSums)
F(:,i) = F(:,i)./columnSums(i);
end
Best wishes
Torsten.

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