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MathGroup Archive 2006

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Re: position lists

  • To: mathgroup at smc.vnet.net
  • Subject: [mg68706] Re: [mg68688] position lists
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Thu, 17 Aug 2006 04:18:13 -0400 (EDT)
  • Reply-to: hanlonr at cox.net
  • Sender: owner-wri-mathgroup at wolfram.com

a = {1, 1, 2, 2, 1, 4};

Flatten/@(Position[a,#]&/@
        Range[Max[a]])/.{}:>{0}

{{1,2,5},{3,4},{0},{6}}


Bob Hanlon

---- rych <rychphd at gmail.com> wrote: 
> have
>   In: a = {1, 1, 2, 2, 1, 4}
> want
>   {{1, 2, 5}, {3, 4}, {0}, {6}};
> 
> more effectively than just
>   In: Position[a, #] & /@ Range[4]
>   Out: {{{1}, {2}, {5}}, {{3}, {4}}, {}, {{6}}}
> 
> Ideas? Known one-liners?
> Thanks
> Igor
> 


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