nextcombi

Given a set of N items, iterate over all the combinations of size R (R<N)

Description

Given a set of N items, we want to do something with all possible subsets of that set which have size K. This method iterates over those subsets in a deterministic fashion. Unlike "nchoosek" (which can return a list of all such combinations) the list of possible combinations is never generated in memory, meaning it should be possible to apply this to quite large K.

Example: to print all combinations of 6C3:

a = 1:3;
while a
  disp(a);
  a = nextcombi(6, a);
end

The complexity of nextcombi is O(N), so the iteration of all combinations should be O(N * nchoosek(N,K)).

• MATLAB release: MATLAB 7.4 (R2007a)

[John D'Errico]

See my loopchoose, which does the same thing.

http://www.mathworks.com/matlabcentral/fileexchange/loadFile.do?objectId=13276&objectType=FILE