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Re: Sorting 3 points

  • To: mathgroup at smc.vnet.net
  • Subject: [mg87984] Re: Sorting 3 points
  • From: Alexey Popkov <popkov at gmail.com>
  • Date: Mon, 21 Apr 2008 06:50:41 -0400 (EDT)
  • References: <fuhfa6$ibk$1@smc.vnet.net>

On 21 =C1=D0=D2, 11:21, car... at colorado.edu wrote:
> Simple question, but documentation is no help.
> I have three coordinate triplets:
>
> =9AP1={x1,y1,z1} =9A =9A =9AP2={x2,y2,z2} =9A =9A =9AP3={x3,y3,z3}
>
> where all entries are numeric. I wont to sort them into
>
> =9AP1s={xs1,ys1,zs1} P2s={xs2,ys2,zs2} P3s={xs3,ys3,zs3}
>
> so that zs3>=zs2>=zs1, with one command
>
> =9A =9A{P1s,P2s,P3s}=Sort[{P1,P2,P3}, Ordering Function]
>
> Is that possible and if so, which Ordering Function
> should be used? =9AThanks.


The simplest solution is to use SortBy
{P1s,P2s,P3s}=SortBy[{P1,P2,P3},#[[3]]&]
or
{P1s,P2s,P3s}=SortBy[{P1,P2,P3},Last]


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