How to make combinations of given condition?

Hi, all,

For example, if I want to make all combination of 5-dim vectors have only 2 two's, other entries are all 0. Is there a command in Matlab can do it? That is 22000 20200 20020 20002 02200 02020 02002 00220 00202 00022

Thanks.

Answer 1

[Andrei Bobrov]

k = dec2bin(0:sum(pow2(0:4)))-'0';
out = 2*k(sum(k,2) == 2,:);

[C Zeng]

Andrei, thanks, can you explain?

Actually I want all other entries to be 1. Is there a way to do it easily?

I tried your code, it works here though not understood here. :-(

Answer 2

[Roger Stafford]

This is a problem for matlab's 'nchoosek' function.

[C Zeng]

Thanks, got it!