Guys, looking at some old code I had I found this function, which gives you all the possible combinations of k elements from a lis of n objects. For example: <hansl> function matrix choose(matrix from, scalar h) if h <= 0 ret = {} elif h == 1 matrix ret = vec(from) else ret = {} from = vec(from) n = rows(from) loop i = 1 .. n-h+1 --quiet x = from[i] matrix c = selifr(from, (seq(1,n)' .> i)) if rows(c) > 0 matrix ret |= x ~ choose(c, h-1) endif endloop endif return ret end function eval choose(seq(1,4), 2) </hansl> returns <output> 1 2 1 3 1 4 2 3 2 4 3 4 </output>. My question is: I was under the impression that we alreasy added something like this, but I can't find it either among the native functions, nor in the extra package. Any hint? ------------------------------------------------------- Riccardo (Jack) Lucchetti Dipartimento di Scienze Economiche e Sociali (DiSES) Università Politecnica delle Marche (formerly known as Università di Ancona) r.lucchetti(a)univpm.it http://www2.econ.univpm.it/servizi/hpp/lucchetti -------------------------------------------------------