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MathGroup Archive 2005

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Re: element selection

  • To: mathgroup at smc.vnet.net
  • Subject: [mg53630] Re: [mg53605] element selection
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Fri, 21 Jan 2005 06:35:36 -0500 (EST)
  • Reply-to: hanlonr at cox.net
  • Sender: owner-wri-mathgroup at wolfram.com

n=100000;

x=Sort[Table[Random[Integer,{0,10000}],{n}]];

y=Sort[Table[Random[Integer,{0,10000}],{n}]];

comp[x_?VectorQ,y_?VectorQ, maxDif_] :=
    Select[Thread[{x,y}],
        Abs[#[[1]]-#[[2]]]<=maxDif&] /; 
      Length[x]==Length[y];

Timing[Length[comp[x,y,2]]]

{2.04 Second,16650}


Bob Hanlon

> 
> From: "Bruyndonckx P." <pbruynd at vub.ac.be>
To: mathgroup at smc.vnet.net
> Date: 2005/01/20 Thu AM 03:47:45 EST
> To: mathgroup at smc.vnet.net
> Subject: [mg53630] [mg53605] element selection
> 
> 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.
> 
> Thx,
> 
> Peter
> 
> 


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