Re: Building a list

*To*: mathgroup at smc.vnet.net*Subject*: [mg47131] Re: Building a list*From*: bobhanlon at aol.com (Bob Hanlon)*Date*: Sat, 27 Mar 2004 01:34:34 -0500 (EST)*References*: <c40sfi$mp8$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Outer is what you want xlist={x1,x2,x3}; Outer[f[a,b,#1,#2]&, xlist, xlist ] {{f[a, b, x1, x1], f[a, b, x1, x2], f[a, b, x1, x3]}, {f[a, b, x2, x1], f[a, b, x2, x2], f[a, b, x2, x3]}, {f[a, b, x3, x1], f[a, b, x3, x2], f[a, b, x3, x3]}} Bob Hanlon In article <c40sfi$mp8$1 at smc.vnet.net>, Mark Coleman <mark at markscoleman.com> wrote: << I've got a relatively simple function f[a_,b_,c_,d_], where a and b are integers and c and d are lists (of reals), and f returns a real. I need to evaluate f on (potentially long) sets of lists and calculate a square "matrix" from the possible permutations of the elements in the lists. For instance If xlist={x1,x2,x3} I need to calculate {{f[a,b,x1,x1],f[a,b,x1,x2],f[a,b,x1,x3]},{f[a,b,x2,x1],f[a,b,x2,x2],f[a ,b,x2,x3]},{f[a,b,x3,x1],f[a,b,x3,x2],f[a,b,x3,x3]}} Note that f[a,b,c,d] does not equal f[a,b,d,c]. My first reaction was that Outer[] might do this, but I cannot seem to get it to work. I'd appreciate any suggestions.