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MathGroup Archive 2005

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Re: Sorting on multiple columns within a matrix

  • To: mathgroup at smc.vnet.net
  • Subject: [mg57837] Re: Sorting on multiple columns within a matrix
  • From: "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de>
  • Date: Thu, 9 Jun 2005 06:12:01 -0400 (EDT)
  • Organization: Uni Leipzig
  • References: <d892lm$sc6$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

Sort[M, If[#1[[2]] =!= #2[[2]], #1[[2]] < #2[[2]], 
#1[[1]] < #2[[1]]] &]

??

Regards

  Jens

"Lee Newman" <leenewm at umich.edu> schrieb im 
Newsbeitrag news:d892lm$sc6$1 at smc.vnet.net...
> Hello,
>
> I can't come up with a solution to the following 
> simple task:
>
> -  I have a matrix, let's M={ 
> {"Z",2,"a"},{"A",2,"k"}, {"Z",1,"z"},
> {"A",1,"a"},{"Z",3,"k"}, {"A",3,"z"} }
> -  I want to be able to sort the matrix 
> row-wise, based on multiple
> columns, for example sort first on column 2 
> (ascending) and then
> secondly on column1 (ascending)
>
> desired result:
> A 1 a
> Z 1 z
> A 2 k
> Z 2 a
> A 3 z
> Z 3 k
>
> I suspect the solution involves using a pure 
> function of some form as
> the second argument in the Sort function, but I 
> can't figure out what
> this function should be.
>
> Thanks,
> Lee
> 



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