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

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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?

Answers (1)

Matt J
Matt J on 2 Dec 2012
Use NCHOOSEK
  2 Comments
Christos
Christos on 2 Dec 2012
nchoosek returns the number of possible drawings n from k. I dont see how i could use it.
Matt J
Matt J on 2 Dec 2012
Edited: Matt J on 3 Dec 2012
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

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