MATLAB: Select specific number of random ones placed in a zeros matrix

binarymatrixmatrix manipulationoneszeros

Hi guys, I am trying to make a 1024 by 1024 zeros matrix with specifically 20 ones randomly placed anywhere within the zeros matrix. I feel like it's easy but can anyone help?

Best Answer

m = zeros(1024, 1024);
m(randperm(numel(m), 20)) = 1;  %place 20 ones randomly in m.

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MATLAB: Symmetric binary matrix with diagonal 0 values

Guaranteed to work on the first try:

Msize = 10;  %size of square matrix
N = 20; %number of ones on each side of the diagonale
M = zeros(Msize);
indices = nonzeros(tril(reshape(1:Msize^2, Msize, Msize), -1));  %get indices BELOW diagonale
M(indices(randperm(numel(indices), N))) = 1;  %pick N indices and fill with 1
M = M | M.'   %do the symmetry

MATLAB: Select some elements from a given matrix

Assuming you don't care about the order in which they are selected:

m(randperm(numel(m),3))

If you want to preserve the original ordering, then:

m(sort(randperm(numel(m),3)))

Best Answer

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MATLAB: Symmetric binary matrix with diagonal 0 values

MATLAB: Select some elements from a given matrix

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