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Re: Sorting 3 points

  • To: mathgroup at smc.vnet.net
  • Subject: [mg87988] Re: [mg87935] Sorting 3 points
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Mon, 21 Apr 2008 14:35:47 -0400 (EDT)
  • Reply-to: hanlonr at cox.net

p = {P1,P2,P3};

Sort[p, #1[[3]] < #2[[3]] &]

Sort[p, Last[#1] < Last[#2] &]


Bob Hanlon

---- carlos at Colorado.EDU wrote: 
> Simple question, but documentation is no help.
> I have three coordinate triplets:
> 
>  P1={x1,y1,z1}      P2={x2,y2,z2}      P3={x3,y3,z3}
> 
> where all entries are numeric. I wont to sort them into
> 
>  P1s={xs1,ys1,zs1} P2s={xs2,ys2,zs2} P3s={xs3,ys3,zs3}
> 
> so that zs3>=zs2>=zs1, with one command
> 
>    {P1s,P2s,P3s}=Sort[{P1,P2,P3}, Ordering Function]
> 
> Is that possible and if so, which Ordering Function
> should be used?  Thanks.
> 



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