How to create a random binary matrix with equal number of ones in each column and equal number of 1 in each row ?

Question

Raghwan Chitranshu 2019-1-13

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https://ww2.mathworks.cn/matlabcentral/answers/439541-how-to-create-a-random-binary-matrix-with-equal-number-of-ones-in-each-column-and-equal-number-of-1

回答： Bruno Luong 2019-1-13

Hi All,

I want to create a random binary matrix with equal number of ones in each column and also equal number of ones in each row.

Appreciate if anyone have an idea to implement this in Matlab.

Thanks.

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Stephen23 2019-1-13

https://www.mathworks.com/matlabcentral/answers/337211-how-to-create-random-binary-matrix-with-specified-number-of-ones-in-each-row-and-column

Raghwan Chitranshu 2019-1-13

@Madhan thanks for the comment .

Basically I am looking to construct a matrix with these conditions

no all 0 coulmns
every column contains an odd number of 1's
the number od 1's in each row of the matrix should be made equal or as close as possible to the average (total number of 1's in matrix divided by number of rows)

if you can help regarding this

Regards

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Answer 1

Walter Roberson 2019-1-13

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https://ww2.mathworks.cn/matlabcentral/answers/439541-how-to-create-a-random-binary-matrix-with-equal-number-of-ones-in-each-column-and-equal-number-of-1#answer_356191

在 MATLAB Online 中打开

N = 10;   %number of 1s to place
M = 20;   %dimension of matrix
maxtries = 10;   %random placement can fail. How often to retry ?
for trynum = 1 : maxtries
    L = zeros(M,M);
    failed = false;
    for K = 1 : M*N
        cmask = sum(L) < N;
        rmask = sum(L,2) < N;
        locs = find(cmask & rmask & L ~= 1);   %implicit expansion used!
        if isempty(locs)
            fprintf('try %d boxed in at iteration %d\n', trynum, K);
            failed = true;
            break;
        end
        thisloc = locs( randi(length(locs)) );
        L(thisloc) = 1;
    end
    if ~failed
        fprintf('try %d worked\n', trynum);
        display(L)
        break;
    end
end
if failed
    fprintf('Did not succeed in %d tries. You could increase maxtries, but are you sure there is a way to succeed?\n', maxtries);
end

My tests show that with this particular combination, 10 of 20, that success rate in placing within 10 tries is roughly 50% -- suggesting that maxtries should perhaps be increased.