Find the first N non-zero elements in each row of a matrix

Question

I have a matrix in MATLAB with zeroes and I would like to get another matrix with the first N non-zero elements in each row. Let\'s say for example N = 3<

Answer 1

Using accumarray with no loops:

N = 3;
[ii,jj] = find(A); [ii,inds]=sort(ii); jj = jj(inds);
lininds = ii+size(A,1)*(jj-1);
C = accumarray(ii,lininds,[],@(x) {A(x(1:N)')}); %' cell array output
B = vertcat(C{:})
B =
     2     6     7
     3     2     4
     1     3     4
     1     2     1