Hi lucksBi, the find command gives you the row and column indices for a given condition. The find command searches column by column but you are more interested in row by row, so in this case it's better to use the transpose of the matrix
[a b] = find(matrix.'==0];
inds = [b a]
inds =
1 2
1 3
1 5
1 6
2 5
3 2
3 6
