One way based around ndgrid:
>> M = [10 1 9; 1 5 4; 2 1 5];
>> N = M.';
>> S = size(N);
>> [R,C] = ndgrid(1:S(1),1:S(2));
>> [C(:),R(:),N(:)]
ans =
1 1 10
1 2 1
1 3 9
2 1 1
2 2 5
2 3 4
3 1 2
3 2 1
3 3 5
If the order is not important then you do not need the transpose. Note that in MATLAB the first dimension is down the columns.
