Matlab：如何从2个向量中找到所有可能的组合？

Question

V1 and V2 are vectors 1x20 and 1x10 respectively.

How to find all possible combinations of 15 elements from V1 and 3 elements from V2 ?

The order of the selected elements is not important.

Answer 1

Here is one way:

% n-choose-k from each vector
A = nchoosek(1:20,15);
B = nchoosek(1:10,3);

% all combinations from the two sets
[X,Y] = ndgrid(1:size(A,1), 1:size(B,1));
C = [A(X(:),:) B(Y(:),:)];

The result contains the indices from the two vectors V1 and V2:

>> whos C
  Name            Size                Bytes  Class     Attributes

  C         1860480x18            267909120  double    

---

If you want to directly apply it to the actual vectors, replace the first two lines with:

A = nchoosek(V1,15);    % V1 is a 1x20 vector
B = nchoosek(V2,3);     % V2 is a 1x10 vector