Question

I would like to generate all possible combinations for selecting rows in batches of lets say ‘k’ size. For example, matrix A has 3 rows and I want all combinations for batch size 2, i.e. rows (1,2)(1,3)(2,3). What would be the simplest way to do it? Then I would like use them for some operation like myfunction();

I think nchoosek function does the trick of selecting the combination but then how can I use each row of the output from nchoosek as index for my matrix?

Answer 1

If you want to use each combination one by one you can do something like this:

A = rand(3);
comb = nchoosek(length(A), 2);
for i = 1:size(comb, 1)
  myfunction(A(comb(i, :), :));
end

A(comb(i, :)) is a k x n matrix (here 3 x 2) corresponding to the i-th combination of rows.