MATLAB: Select random data from a matrix and replace it

Question

Hello,

I have the following problem: I have a matrix e.g

1 0 1 0 1
1 1 1 0 0
1 1 1 1 1
1 1 0 0 1

and I try to do this: When the sum of each column exceeds the threshold=4 some random "1" of the column that goes beyond the threshold become zero. How do I implement this in matlabThis can be done without using loops?I would be very grateful if someone helpend me

Answer 1

A = [1 0 1 0 1
1 1 1 0 0
0 0 0 0 0
1 1 1 1 1
1 1 0 0 1
0 0 0 0 0];
p = 4;
[ii,jj] = find(A);
jjj = accumarray(ii,jj,[size(A,1),1],@(x){x(randperm(numel(x),min(numel(x),p)))});
k = cellfun(@numel,jjj);
out = accumarray([repelem((1:numel(k))',k),cell2mat(jjj)],1,size(A));