KCOMBSN

C = KCOMBSN(N,k,p) returns the k-by-p matrix C consisting of k random combinations of p unique integers between 1 and N.
Note that:
1. N, k and p should be positive integers, with p < N.
2. There are at most nchoosek(N,p) combinations of p unique integers between 1 and N, therefor k <= nchoosek(N,p).
Example: The following code:
N = 9;
k = 3;
p = 4;
C = kcombsn(N,k,p);

could return the following matrix C:

5 3 9 6
1 6 5 2
5 6 4 2

NB: This code circumvents taking a subset of all possible combinations, as constructing all possible combinations, e.g. using nchoosek(1:N,p), easily runs into memory issues.