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MathGroup Archive 2004

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Re: extracting a list to a list, help please

  • To: mathgroup at smc.vnet.net
  • Subject: [mg46235] Re: extracting a list to a list, help please
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Thu, 12 Feb 2004 07:16:00 -0500 (EST)
  • Organization: Universitaet Leipzig
  • References: <c07p1q$kk7$1@smc.vnet.net>
  • Reply-to: kuska at informatik.uni-leipzig.de
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

use one of the variants below

Take[#, 2] & /@ mylist1

Drop[#, -2] & /@ mylist1

mylist1 /. {a_?AtomQ, b_, ___} :> {a, b}

Part[#, {1, 2}] & /@ mylist1

Transpose[Take[Transpose[mylist1], 2]]


Regards
  Jens

Serge wrote:
> 
> Hello,
> 
> I am a beginner in Mathematica and I have a rather simple question. I
> made some calculations that I need for an orbit and I have a list that
> look like this:
> 
> mylist1 = {{a1,b1,c1,d1},{a2,b2,c2,d2},{a3,b3,c3,d3},etc}
> 
> All I want to do is to make a list of the form
> 
> mylist2 = {{a1,b1},{a2,b2},{a3,b3},etc}
> 
> from the original list (mylist1),
> 
> so that I can ListPlot those pairs of points (they represent x and y
> coordinates for some orbit). I am having trouble figuring out how to do
> this. I tried using the Table command but I couldn't get it into the
> above form. I would greatly appreciate if someone can help me out.
> Thanks so much.
> 
> Best,
> Serge


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