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MathGroup Archive 2004

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Re: Building a list

  • To: mathgroup at smc.vnet.net
  • Subject: [mg47134] Re: Building a list
  • From: Roland Franzius <roland.franzius at uos.de>
  • Date: Sat, 27 Mar 2004 01:34:36 -0500 (EST)
  • Organization: Universitaet Hannover
  • References: <c40sfi$mp8$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Mark Coleman wrote:
> 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.

Is

Outer[f[a, b, #1, #2] &, {x1, x2, x3}, {x1, x2, x3}]

what fits your need?

-- 

Roland Franzius


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