A = [12 0 0
0 0 0
0 13 0
0 0 0
0 0 0
0 0 11];
% scan each row of A
for ii = 1:size(A,1)
% find the index of non-zero elements in the row
idx = find(A(ii,:));
% if there are none (the row is all zeros)
if isempty(idx)
% if it's not the first row
if ii > 1
% find the index of non-zero elements in the previous row
idx = find(A(ii-1,:));
% set the elements at those indices in this row to 1
A(ii,idx) = 1;
end
else % if there are some non-zero elements in the row, set them to 1
A(ii,idx) = 1;
end
end
A
