How to randomly choose 5% of a matrix to be of value 1.

I have a 256 x 256 matrix which has value 1 inside a small square 20 x 20 around the center, and zero elsewhere. I need to randomly choose say 5% elsewhere to be 1 also. How do I go about this?

Thank you.

Answer 1

[Walter Roberson]

candidates = find(~YourMatrix);
ncand = length(candidates);
locs = randperm( ncand, round(ncand * 0.20) );
YourMatrix(locs) = 1;

[Gideon Idumah]

Works perfectly.

Thank you.