Re: Multiplying permutations
- To: mathgroup at smc.vnet.net
- Subject: [mg41747] Re: [mg41723] Multiplying permutations
- From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
- Date: Wed, 4 Jun 2003 08:34:33 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
On Tuesday, June 3, 2003, at 08:13 pm, Dr. Wolfgang Hintze wrote:
> Is there a simple command in Mathematica to multiply two permutations,
> i.e. to carry out one after the other?
>
> I looked at the packages DiscreteMath`Permutations` and
> DiscreteMath`Combinatorica` but couldn't find it.
>
> Example
>
> p = {3,1,2} mapping: 1->3, 2->1, 3->2
> q = {2,1,3} mapping: 1->2, 2->1, 3->3
> p.q = mappings (p first, then q)
> [1-p->3-q->3, 2-p->1-q->2, 3-p->2-q->1]
> = {3,2,1}
>
> Any help appreciated
>
> Wolfgang
>
>
>
If you load in the DiscreteMath`Combinatorica` package then
Permute[x,y] will give you the product of two permutations x and y. e.g.
In[18]:=
<<DiscreteMath`Combinatorica`
In[22]:=
Permute[{3,1,2},{2,1,3}]
Out[22]=
{1,3,2}
In[23]:=
Permute[{2,1,3},{3,1,2}]
Out[23]=
{3,2,1}
Andrzej Kozlowski
Yokohama, Japan
http://www.mimuw.edu.pl/~akoz/
http://platon.c.u-tokyo.ac.jp/andrzej/