function sub_s=subsets1(s,k)
% SUBSETS1 creates sub-sets of a specific from a given set
% SS = subsets1(S, k)
% 
% S is the given set
% k is the required sub-sets size
% 
% Example:
% 
% >> ss=subsets1([1:4],3);
% >> ss{:}
% ans =
%      1     2     3
% ans =
%      1     2     4
% ans =
%      1     3     4
% ans =
%      2     3     4
% 
% Written by Raanan Yehezkel, 2004

if k<0 % special case
    error('subset size must be positive');
elseif k==0 % special case
    sub_s={[]};
else
    l=length(s);
    ss={};
    if l>=k
        if k==1 % Exit condition
            for I=1:l
                ss{I}=s(I);
            end
        else
            for I=1:l
                ss1=subsets1(s([(I+1):l]),k-1);
                for J=1:length(ss1)
                    ss{end+1}=[s(I),ss1{J}];
                end
            end
        end
    end
    sub_s=ss;
end