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MathGroup Archive 1997

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Re: How to select unique elements in a list?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg7987] Re: How to select unique elements in a list?
  • From: crose at c2.telstra-mm.net.au (Colin Rose)
  • Date: Wed, 30 Jul 1997 23:57:38 -0400
  • Organization: Theoretical Research Institute
  • Sender: owner-wri-mathgroup at wolfram.com

"Carl Woll" <carlw at u.washington.edu> wrote:

  >  First, let me say that Union does not do what I'm looking for! I am
  >  interested in a function which returns the unique elements from a list.
  >  Let's call the function Distinct. Then, I want
  > 
  >  Distinct[{i1,i2,i3,i2}]        to return        {i1,i3}
  

FOLLOWING UP on my previous post:   a neater (and faster) solution is:
________________________________
  

         Y[x_] := Cases[ Split[Sort[x]], {_}]//Flatten

eg:  
 
  In[]   test=Table[ i[Random[Integer,1000]],{1000}];
         Y[test]; // Timing

 Out[]   {0.0333333 Second,Null}          PowerMac 8600/200


Cheerio

Colin

-- 
Colin Rose 
tr(I) - Theoretical Research Institute
______________________________________
crose at c2.telstra-mm.net.au
http://www.usyd.edu.au/su/tri/


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