RE: Building a list

*To*: mathgroup at smc.vnet.net*Subject*: [mg47137] RE: [mg47114] Building a list*From*: "David Park" <djmp at earthlink.net>*Date*: Sat, 27 Mar 2004 01:34:40 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Mark, 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]}} David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ From: Mark Coleman [mailto:mark at markscoleman.com] To: mathgroup at smc.vnet.net Greetings, 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. Thanks, Mark