Re: patterns
- To: mathgroup at smc.vnet.net
- Subject: [mg3750] Re: [mg3727] patterns
- From: Roberto Colistete Junior <roberto at verao.cce.ufes.br>
- Date: Sun, 14 Apr 1996 03:02:33 -0400
- Sender: owner-wri-mathgroup at wolfram.com
Susan Rempe wrote:
>
>
> I have a list of numbers and symbols.
> How can I collect all the members of the list
> which have a common denominator?
>
> ex. list={Sin[theta]/r, Cos[theta]/(r*s), 2*Csc[theta]/(2*r)}
>
> Say I want to collect all members of the list with r in the denominator;
>
> i.e. answer=Sin[theta]/r;
>
> ********************************************
> Susan Rempe *
> University of Washington *
> Department of Chemistry *
> Box 351700 *
> Seattle, WA 98195-1700 *
> *
> (206)685-2951 *
> rempe at u.washington.edu *
> ********************************************
>
>
>
A simple way is to use "Select" and "Denominator" :
In[1]:= list={Sin[theta]/r, Cos[theta]/(r*s), 2*Csc[theta]/(2*r)}
General::spell1:
Possible spelling error: new symbol name "list"
is similar to existing symbol "List".
Sin[theta] Cos[theta] Csc[theta]
Out[1]= {----------, ----------, ----------}
r r s r
In[2]:= answer = Select [list, (Denominator[#] === r)&]
Sin[theta] Csc[theta]
Out[2]= {----------, ----------}
r r
Of course, Mathematica simplified the last member of the list, so the
above answer is correct.
------------------------------------------------------------------------
Roberto Colistete Junior Email : roberto at cce.ufes.br
MSc Physics Student
Departamento de Fisica
Universidade Federal do Espirito Santo
Brasil
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