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MathGroup Archive 2005

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Re: Multiple Sums in Mathematica

  • To: mathgroup at smc.vnet.net
  • Subject: [mg53704] Re: [mg53696] Multiple Sums in Mathematica
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Mon, 24 Jan 2005 03:37:25 -0500 (EST)
  • Reply-to: hanlonr at cox.net
  • Sender: owner-wri-mathgroup at wolfram.com

Presumably, you intend f to be a function of the indices.

multiSum[f_, n_Integer, maxIndex_:M, index_String:"i"]  :=
    Module[{var,k},
      var=ToExpression[Table[index<>ToString[k],{k,n}]];
      Fold[Sum[#1,{#2,1,maxIndex}]&,
        f[Sequence@@var],Reverse[var]]];

multiSum[f,3]

Sum[f[i1, i2, i3], {i1, 1, M}, {i2, 1, M}, {i3, 1, M}]

multiSum[f,3,r]

Sum[f[i1, i2, i3], {i1, 1, r}, {i2, 1, r}, {i3, 1, r}]

multiSum[f,3,M,"k"]

Sum[f[k1, k2, k3], {k1, 1, M}, {k2, 1, M}, {k3, 1, M}]


Bob Hanlon

> 
> From: sbrandt at physics.wustl.edu (Sebastian Brandt)
To: mathgroup at smc.vnet.net
> Date: 2005/01/23 Sun AM 02:02:26 EST
> To: mathgroup at smc.vnet.net
> Subject: [mg53704] [mg53696] Multiple Sums in Mathematica
> 
> Hello,
> 
> I want to perform a nested sum, where the number of summations is not
> specified. I.e., I am looking for a way to implement the sum
> 
> sum[ f, {i1, 1, M}, {i2, 1, M}, ..., {in, 1, M} ]
> 
> Does anbody know how to do this for arbitrary n?
> 
> Regards,
> 
> Sebastian Brandt
> 
> 


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