What you didn't say is that your set of four values is by row. Matlab works by column. You'll make your life much easier if you work the same way as matlab. In this particular case, it would be even easier if you stored your array in columns of 4 rows.
A = [ 1 4 3 4 3 4 5 6 4 5 6 7; 2 3 4 5 3 4 5 6 2 3 4 2]
[~, maxloc] = max(reshape(A', 4, [])); %transpose to work by column instead of row
maxloc = sub2ind([4, numel(maxloc)], maxloc, 1:numel(maxloc));
A = zeros(size(A'));
A(maxloc) = 1;
A = A' %transpose back
Much of the work above is just to get the array in the correct shape and back to the shape you have.
