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MathGroup Archive 2005

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Re: element selection

  • To: mathgroup at smc.vnet.net
  • Subject: [mg53623] Re: element selection
  • From: Roland Franzius <roland.franzius at uos.de>
  • Date: Fri, 21 Jan 2005 06:35:27 -0500 (EST)
  • Organization: Universitaet Hannover
  • References: <csnt7e$4ec$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Bruyndonckx P. wrote:
> I have two long sorted lists of Integers.  If the difference between a number in list 1 and a 
> number in list 2 is less than a certain value, both are selected to create a couple.  I am 
> looking for a fast way to go through both lists and extract these elements to create a new list 
> of couples.  I tried a number of things, but all of them were rather slow so I need some expert 
> advice here.

Depends on your task. If you want pairs at the same index position

Select[Transpose[{list1,list2}],(Abs[Subtract@@#]<crit&)]

If you want all possible ordered pairs

replace "Transpose[{list1,list2}]" by

"Flatten[Outer[pair,list1,list2]]"

-- 

Roland Franzius


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