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MathGroup Archive 2005

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Re: Union using SameTest

  • To: mathgroup at smc.vnet.net
  • Subject: [mg61208] Re: [mg61195] Union using SameTest
  • From: Andrzej Kozlowski <andrzej at yhc.att.ne.jp>
  • Date: Wed, 12 Oct 2005 03:09:05 -0400 (EDT)
  • References: <200510120542.BAA09279@smc.vnet.net>
  • Reply-to: Andrzej Kozlowski <andrzej at akikoz.net>
  • Sender: owner-wri-mathgroup at wolfram.com

On 12 Oct 2005, at 14:42, Jack Goldberg wrote:

> Hi Everyone,
>
> Thanks for all your responses.  I am grateful and somewhat
> mystified.  The solutions
> SameTest->(Abs[#1-#2]<10^-2&)]   was the first thing I tried!  It
> didn't work for me - in fact it gave a strange error message -
> something involving "heads in positions 1 and 2 must be the same".
> This was the reason for my posting.  Well, I tried it again and now
> it works.  At this point I believe that the error has to do with my
> reusing certain names over and over with clearing them.  But I am not
> sure and since I can't reconstruct the error - I'm letting this
> sleeping dog lie.
>
> Thanks again fellas!
>
> Jack
>
>

I doubt that "the error has to do with your reusing certain names  
over and over with clearing them". Rather it is simply this:


In[55]:=
lst = {1.1101, 1.11095, 1.11076, 1.09, 2.3523, 2.352,
     2.35211};



In[56]:=
Union[lst, SameTest -> Abs[#1 - #2] < 10^(-2) & ]

Union::"heads":"Heads Function and List at positions `2  and  `1
are expected to be the same.


Out[56]=
Union[{1.1101, 1.11095, 1.11076, 1.09, 2.3523, 2.352,
    2.35211}, SameTest -> Abs[#1 - #2] < 1/10^2 & ]


while:

In[57]:=
Union[lst, SameTest -> (Abs[#1 - #2] < 10^(-2) & )]

Out[57]=
{1.09, 1.1101, 2.352}

Note the parentheses.


Andrzej Kozlowski
Tokyo, Japan




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