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.