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MathGroup Archive 2005

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Re: How to "search" in a matrix?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg60906] Re: How to "search" in a matrix?
  • From: Peter Pein <petsie at dordos.net>
  • Date: Mon, 3 Oct 2005 04:06:04 -0400 (EDT)
  • References: <dhnt71$1hu$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Renan schrieb:
> I have this matrix:
> 
> matr = {{a, b, 1}, {c, d, 2}, {e, f, 3}}
> 
> I'm trying to do a "search" in a matrix. The "real" matrix will contain strings.
> How to "search" for a given value in a matrix and return all lines that have it?
> 
> 'Select' seems to handle only lists - and this would require a
> Flatten, probably making my code too complicated and maybe slow (the
> real matrix will contain something like 100 elements - weather data).
> 
> Thanks.
> 
Hi Renan,

a matrix _is_ a list (of lists):

In[1]:= matr={{a,b,1},{c,d,2},{e,f,3}};
In[2]:= MemberRow[m_,el_]:=Select[m,MemberQ[#,el]&]
In[3]:= MemberRow[matr,f]
Out[3]= {{e,f,3}}
In[4]:= MemberRow[Append[matr,{b,a,4}],b]
Out[4]= {{a,b,1},{b,a,4}}

Peter


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