matthiasm@8: function sub_s=subsets1(s,k)
matthiasm@8: % SUBSETS1 creates sub-sets of a specific size from a given set
matthiasm@8: % SS = subsets1(S, k)
matthiasm@8: % 
matthiasm@8: % S is the given set
matthiasm@8: % k is the required sub-sets size
matthiasm@8: % 
matthiasm@8: % Example:
matthiasm@8: % 
matthiasm@8: % >> ss=subsets1([1:4],3);
matthiasm@8: % >> ss{:}
matthiasm@8: % ans =
matthiasm@8: %      1     2     3
matthiasm@8: % ans =
matthiasm@8: %      1     2     4
matthiasm@8: % ans =
matthiasm@8: %      1     3     4
matthiasm@8: % ans =
matthiasm@8: %      2     3     4
matthiasm@8: % 
matthiasm@8: % Written by Raanan Yehezkel, 2004
matthiasm@8: 
matthiasm@8: if k<0 % special case
matthiasm@8:     error('subset size must be positive');
matthiasm@8: elseif k==0 % special case
matthiasm@8:     sub_s={[]};
matthiasm@8: else
matthiasm@8:     l=length(s);
matthiasm@8:     ss={};
matthiasm@8:     if l>=k
matthiasm@8:         if k==1 % Exit condition
matthiasm@8:             for I=1:l
matthiasm@8:                 ss{I}=s(I);
matthiasm@8:             end
matthiasm@8:         else
matthiasm@8:             for I=1:l
matthiasm@8:                 ss1=subsets1(s([(I+1):l]),k-1);
matthiasm@8:                 for J=1:length(ss1)
matthiasm@8:                     ss{end+1}=[s(I),ss1{J}];
matthiasm@8:                 end
matthiasm@8:             end
matthiasm@8:         end
matthiasm@8:     end
matthiasm@8:     sub_s=ss;
matthiasm@8: end