How to select all subset of rows of a matrix given the size of subset

Hi, i want to select all possible submatrices of rows -subsets of a matrix given the size of subset. i.e if i have the matrix X=[1 2 3;4 5 6; 7 8 9] i want to give k=2 (for example) and get

x1=[1 2 3;4 5 6] x2=[1 2 3;7 8 9] x3=[4 5 6;7 8 9].

This is an example. Is there a built-in or something for this?

Answer 1

[Matt J]

Use NCHOOSEK

[Christos]

nchoosek returns the number of possible drawings n from k. I dont see how i could use it.

[Matt J]

It can also perform drawings, as shown in the following example in which I compute all of the length k=2 drawings of 1:n, with n=4. You should ponder how this could be applicable to you.

>> nchoosek(1:4,2)

ans =

       1     2
       1     3
       1     4
       2     3
       2     4
       3     4