npermutek

permutes k elements from the vector v

NPERMUTEK - permutations without repetitions.
This function A = npermutek(v,k) returns all the possible permutations
of k elements from the vector v without repetitions. k should be less than
or equal to number of elements in v.
The function [A, I] = npermutek(v,k) returns both the matrix and indeces
of the permuted matrix, such that A = v(I). Both matrices will be of the
size nPk-by-k where k = numel(v).

Examples:

v = 1:4;
k = 3;
A = npermutek(v,k); % returns 24-by-3 matrix
1 2 3
1 2 4
1 3 2
1 3 4
1 4 2
1 4 3
2 1 3
2 1 4
2 3 1
2 3 4
2 4 1
2 4 3
3 1 2
3 1 4
3 2 1
3 2 4
3 4 1
3 4 2
4 1 2
4 1 3
4 2 1
4 2 3
4 3 1
4 3 2

v = 'abc';
k = 2;
[A,I] = npermutek(v,k) % returns 6-by-2 char array

'ab'
'ac'
'ba'
'bc'
'ca'
'cb'

and 6-by-2 matrix

1 2
1 3
2 1
2 3
3 1
3 2