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Re: A Question about Combinatorica

  • To: mathgroup at smc.vnet.net
  • Subject: [mg102722] Re: [mg102714] A Question about Combinatorica
  • From: Tomas Garza <tgarza10 at msn.com>
  • Date: Sat, 22 Aug 2009 03:36:11 -0400 (EDT)
  • References: <200908210842.EAA13961@smc.vnet.net>

The first question you must ask the author of the book you mention.

Number of combinations of n objects taken in sets of k, is that what you mean?
The answer to that is n!/k! (n-k)!

The actual combinations carry in Mathematica the strange name of KSubsets, and in order to calculate them  you must FIRST call the Combinatorica package: thus

In[1]:= <<Combinatorica`

In[2]:= KSubsets[{"A","B","C","D"},3]
Out[2]= {{A,B,C},{A,B,D},{A,C,D},{B,C,D}}

Tomas Garza




> Date: Fri, 21 Aug 2009 04:42:27 -0400
> From: m.a.elwahaab at gmail.com
> Subject: [mg102714] A Question about Combinatorica
> To: mathgroup at smc.vnet.net
>
> Dear Sir,
>
> I have a question about Combinatorics.
>
> If we have four different letters as A, B, C, D .
>
> A text book mentions that Q(4,4)/2 = 3 different combinations. What the
> meaning of Q & why division by 2 ?
>
> How can I do this by Mathematica with combinatorica package?
>
> I need really for your advice
>
> Thanks too much
>
> *Marwa Ali Abd El Wahaab*
> *Teaching Assistant *
> Faculty of Engineering
> Mansoura University
>
>


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