Create matrix with indices of all unique combinations

Say I have a vector ind = 1:4 and want to create a mx4 matrix of zeros and ones that represetns all unique combinations of these four indices, where m is the number of unique combinations, 16 in this case. So, the first few rows should look like like this:

A(1:7,:) = [0 0 0 0;
            1 0 0 0;
            0 1 0 0;
            0 0 1 0;
            0 0 0 1;
            1 1 0 0;
            1 0 1 0]

I noticed that the rows corresponds to the binary representation of the range 0:15. I tried using dec2bin(0:15) but this gives a gives a character vector. It can probably be converted to what I want, but I feel this is not the most efficient and elegant way of doing it.

Answer 1

[Ameer Hamza]

You can use dec2bin() like this

n = 4;
M = dec2bin(0:2^n-1)-'0';

Other then that, the easiest might be combvec() from deep learning toolbox

n = 4;
C = repmat({[0 1]}, 1, n);
M = combvec(C{:}).';

If you don't have the toolbox

n = 4;
C = repmat({[0 1]}, 1, n);
Cg = cell(size(C));
[Cg{:}] = ndgrid(C{:});
Cg = cellfun(@(x) {x(:)}, Cg);
M = cell2mat(Cg);

[Alexander van Saase]

Your first solution is a bit of a hack, but works perfectly and with the least amount of code. Thanks!

[Ameer Hamza]

I am glad to be of help!