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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: [mg46176] Re: [mg46155] extracting a list to a list, help please
  • From: Oleksandr Pavlyk <pavlyk at phys.psu.edu>
  • Date: Tue, 10 Feb 2004 00:05:43 -0500 (EST)
  • Organization: Penn State University; Department of Physics
  • References: <200402091054.FAA20948@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi Serge,

You have to use

mylist2 = Map[ Take[#1, 2]&, mylist1 ];

Take[ someList, 2]  returns first two elements of that list.
Notice, that mylist1 is a list, elements of which are lists
themselves. So Map will apply Take function to each element of mylist1.

Regards,
Sasha

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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