The solution is probably simple but I need someone to point me to it. How can I reduce the following 6 permutations to the 3 unique combinations (1,1,0) (1,0,1) (0,1,1)? permn(c(1,1,0)) [[1]] [1] 1 1 0 [[2]] [1] 1 0 1 [[3]] [1] 0 1 1 [[4]] [1] 0 1 1 [[5]] [1] 1 0 1 [[6]] [1] 1 1 0 Thanks a lot Marcelo Jenny