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Re: Cyclic permutations

  • To: mathgroup at smc.vnet.net
  • Subject: [mg79410] Re: [mg79377] Cyclic permutations
  • From: DrMajorBob <drmajorbob at bigfoot.com>
  • Date: Thu, 26 Jul 2007 05:30:12 -0400 (EDT)
  • References: <f7pon7$prc$1@smc.vnet.net> <f7sgu2$ss8$1@smc.vnet.net> <f84juv$qpq$1@smc.vnet.net> <200707250614.CAA23554@smc.vnet.net> <33340097.1185365315232.JavaMail.root@m35>
  • Reply-to: drmajorbob at bigfoot.com

For instance...

perms = {{a, b, c, d}, {a, c, b, d}, {b, c, d, a}};
unsortedUnion[x_] := Tally[x][[All, 1]]
unsortedUnion[perms /. {x__, a, y___} :> {a, y, x}]

{{a, b, c, d}, {a, c, b, d}}

Bobby

On Wed, 25 Jul 2007 04:27:37 -0500, King, Peter R  
<peter.king at imperial.ac.uk> wrote:

> I have a set of permutations eg.
>
> {a,b,c,d}, {a,c,b,d} {b,c,d,a}
>
> Some of which are just cyclic variations of others (ie. {b,c,d,a} is a
> cyclic variant of {a,b,c,d}). Is there a simple way of getting rid of
> these, so that the above set just becomes
>
> {a,b,c,d}, {a,c,b,d}
>
> I am quite happy to select the cyclic variant to be kept arbitrarily (or
> using lexical ordering, I'm not particularly concerned).
>
> Thanks in advance for your help.
>
> Peter King
>
> (by the way I am still using version 5.1 so V6 specific methods wouldn't
> help I'm afraid)
>
>
>



-- 

DrMajorBob at bigfoot.com


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