Find a subset of unique permutations

I have many arrays A of varying length. For any given A, I'd like to find all the unique sets of three elements of A. For example, if A has five elements:

A = [5 6 2 4 7];

one combination of three elements in A is [5 6 2], another combination is [5 6 4], and so on. When I work this out manually I get these combinations:

5 6 2   
5 6   4   
5 6     7
5   2 4  
5   2   7
5     4 7
  6 2 4  
  6 2   7
  6   4 7
    2 4 7

The appearance of the solutions above makes me think there may be a clever way to use an identity matrix, but I can't quite think of how. Or perhaps there's a way to use perms, perhaps with sort and unique?

Can you think of a way to get all 3-element subsets of an array?

[Geoff Hayes]

Chad - why not use nchoosek as

 nchoosek(A,3)

which returns the same ten subsets that you have shown above. Is using this function undesirable because of its limitations with larger arrays?

[Joseph Cheng]

hmm... well to use what you ask i've only gotten this far

A=[5 6 2 4 7]
pA = perms(A);
sA = sort(pA(:,1:3),2);
uA =unique(sA,'rows')

but it wouldn't be in the same number order of A.

[Chad Greene]

nchoosek it is. Somehow I'd never heard of that function. Thanks Geoff and Joseph!

Answer 1

[Jos (10584)]

Why not use NCHOOSEK?

A = [5 6 2 4 7]; 
nchoosek(A,3)

ans =

       5     6     2
       5     6     4
       5     6     7
       5     2     4
       5     2     7
       5     4     7
       6     2     4
       6     2     7
       6     4     7
       2     4     7

[Chad Greene]

Perfect! This function does exactly what I was looking for. Thanks Jos!