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Re: extracting a list to a list, help please

  • To: mathgroup at smc.vnet.net
  • Subject: [mg46173] Re: extracting a list to a list, help please
  • From: bobhanlon at aol.com (Bob Hanlon)
  • Date: Tue, 10 Feb 2004 00:05:40 -0500 (EST)
  • References: <c07p1q$kk7$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

mylist1 = {{a1,b1,c1,d1},{a2,b2,c2,d2},{a3,b3,c3,d3}};

mylist2 = mylist1[[All, {1,2}]]

{{a1, b1}, {a2, b2}, {a3, b3}}

mylist2 == (Take[#, 2]& /@ mylist1)

True

mylist2 == (Drop[#, -2]& /@ mylist1)

True


Bob Hanlon

In article <c07p1q$kk7$1 at smc.vnet.net>, Serge <nospam at nospam.com> wrote:

<< 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. 


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