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MathGroup Archive 2006

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Re: Selecting Many Things Rather Than Selecting One Thing From Many

  • To: mathgroup at smc.vnet.net
  • Subject: [mg66198] Re: Selecting Many Things Rather Than Selecting One Thing From Many
  • From: dh <dh at metrohm.ch>
  • Date: Thu, 4 May 2006 05:19:41 -0400 (EDT)
  • References: <e39k7e$cno$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi Gregory,
try:
Select[theMatrix, MemberQ[K,#[[1]]]& ]

Daniel

Gregory Lypny wrote:
> Hello everyone,
> 
> I've discovered another use or need for the Select function, which I  
> suspect requires mapping of some sort.
> 
> In my previous posts, members of this MathGroup kindly showed me how  
> to apply Select to many columns of a matrix at once.  For example,
> 
> (Select[#1, #1 > K & ] & ) /@ Transpose[theMatrix]
> 
> will pull out all values greater than K, where K is a number such as  
> 100.
> 
> But suppose now that K is a list of numbers, such as K={34, 876,  
> 199}, and I simply want to extract or identify all of the rows in the  
> first column of theMatrix equal to any one of those numbers.  How  
> would I do that?  I started with
> 
> Select[theMatrix, #[[1]]==any element of list K]
> 
> and I imagine something similar could be applied to the Position  
> function.
> 
> Any hint would be much appreciated.
> 
> 	Gregory
> 


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