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MathGroup Archive 2000

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Re: Mapping down two lists

  • To: mathgroup at smc.vnet.net
  • Subject: [mg25212] Re: [mg25179] Mapping down two lists
  • From: Andrzej Kozlowski <andrzej at tuins.ac.jp>
  • Date: Fri, 15 Sep 2000 02:21:47 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Maybe the following is a little nicer:

Plus @@ First[Transpose[l1 - l2]]^2

Andrzej


-- 
Andrzej Kozlowski
Toyama International University, JAPAN

For Mathematica related links and resources try:
<http://www.sstreams.com/Mathematica/>



on 9/13/00 10:24 AM, John Satherley at js1 at liverpool.ac.uk wrote:

> Hi MathGroup
> I'm trying to sharpen up my functional programming skills and have come
> across a problem which is probably very trivial but I can't find a
> satisfactory solution.
> 
> I have two lists of equal length, one 2 dimensional and the other 1
> dimensional:
> lst1={{1,2},{2,3},{1,3},......}
> lst2={1,2,2,3,4,5.....}
> 
> What I want to do is find the difference between lst1[[i,1]] and lst2[[i]]
> square it and then sum up all the terms over the length of the list.
> 
> It is easy to do this in terms of Tables but I'm trying to find a fast
> solution for long lists that uses map and other functional programming
> tools.
> 
> The best I have come up with is:
> Apply[Plus,([#[[1]]&/@lst1-lst2)^2]
> but I'm wondering if it is possible to map directly onto the two lists
> without first having to extract the elements of the first list? Map seems to
> only work down a single list.
> 
> I would be most grateful of any hints as to how this might be performed in
> an efficient manner.
> 
> Thanks for help
> Dr. John Satherley
> Dept of Chem
> University of Liverpool
> Liverpool L69 7ZD
> UK
> js1 at liv.ac.uk
> 
> 
> 
> 



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