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MathGroup Archive 2005

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SameTest in Union

  • To: mathgroup at smc.vnet.net
  • Subject: [mg61106] SameTest in Union
  • From: Jack Goldberg <jackgoldberg at comcast.net>
  • Date: Mon, 10 Oct 2005 02:40:08 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Hi Folks,

I know there is a simple answer to this question but the help index  
idoes not help!

I have a list, something like this:

lst = {1.1101, 1.11095, 1.11076, 1.09, 2.3523, 2.352. 2.35211}

I want to remove from the list those entries which are near each  
other but not identical, leaving only one representative for each of  
these numbers.  One approach is to use  Union with the option   
SameTest->???.   Here the same test might be that the difference  
between entries is less than, say 10^(-2).   But I can't seem to get  
SameTest to work.  So, what I want is

Union[ lst, SameTest- > ?]

so that  the union returns

{1.1101,  2.35211}

Here, I chose 2 representatives.  Any other choice is OK;   say,

{1.11095,  2.352}

is also satisfactory.

There may be other ways to do this, but I thought of  Union  first.   
Perhaps, Cases  or Select  might be better.  Any help is appreciated.

Jack


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