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MathGroup Archive 2004

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RE: Eliminate duplicates using Union [] in a

  • To: mathgroup at smc.vnet.net
  • Subject: [mg48083] RE: [mg48063] Eliminate duplicates using Union [] in a
  • From: "DrBob" <drbob at bigfoot.com>
  • Date: Tue, 11 May 2004 05:20:06 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Here's Union with "same" meaning identical first and third elements:

test={{a,b,c,d},{d,e,f,g},{a,b,c,g}};
same=#1[[{1,3}]]===#2[[{1,3}]]&;
Union[test,SameTest\[Rule]same]

{{a,b,c,d},{d,e,f,g}}

DrBob

www.eclecticdreams.net


-----Original Message-----
From: Mark Coleman [mailto:mark at markscoleman.com] 
To: mathgroup at smc.vnet.net
Subject: [mg48083] [mg48063] Eliminate duplicates using Union [] in a

I know that if one applies the Union command to a list of values, it 
will return the list with duplicates removed. Can I use the Union 
command to eliminate duplicate when I have a list of data "records"? 
Specifically, I have a large data set that I read into a list on a 
row-oriented basis. Each element of the list consists of another list 
of about 30 different fields. Two of these fields are geographic 
indicators. If two or more records have identical values in these two 
fields, then the full records are considered duplicates and need to be 
identified and removed from the larger list (or at least marked for 
removal). Can Union do this?

Thanks,

-Mark




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