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MathGroup Archive 2003

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Re: simple vactor magitude question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg43811] Re: simple vactor magitude question
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Tue, 7 Oct 2003 02:40:51 -0400 (EDT)
  • Organization: Universitaet Leipzig
  • References: <blj5e0$1dv$1@smc.vnet.net>
  • Reply-to: kuska at informatik.uni-leipzig.de
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

p = Table[Random[], {10}];

and

Sum[p[[i]]*(i-1),{i,1,Length[p]}]

can be written as

MapIndexed[#1*(First[#2] - 1) &, p]

Regards
  Jens


Nathan Moore wrote:
> 
> Suppose I generate a 1-d vecctor of "N" numbers, p[i], and now I want to
> find the sum of (the vector element * index).  I think the syntax should look
> something like,
> 
> Sum[p[i]*i,{i,0,N}]
> 
> but this doesn't seem to be the correct syntax - any help would be
> appreciated.
> 
> Nathan Moore,
> University of Minnesota Physics


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