Re: Dropping Similar Numbers from List
- To: mathgroup at smc.vnet.net
- Subject: [mg60586] Re: [mg60564] Dropping Similar Numbers from List
- From: "David Park" <djmp at earthlink.net>
- Date: Wed, 21 Sep 2005 03:20:19 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
Andre,
Options[Union]
{SameTest -> Automatic}
I'm going to use 10^-12 as a cutoff just so we can better see an example.
testlist = {1, 2, 1, 2, 1, 2} + Table[10*^-13 Random[], {6}]
% // InputForm
{1., 2., 1., 2., 1., 2.}
{1.0000000000005198, 2.000000000000947,
1.0000000000004527, 2.0000000000004654,
1.0000000000003908, 2.0000000000003486}
Union[testlist, SameTest -> (Abs[#1 - #2] < 10*^-12 &)]
{1., 2.}
David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/
From: andre [mailto:erasmus.the.giant at gmail.com]
To: mathgroup at smc.vnet.net
My data set has some numbers which differ by a small amount, say one
part in 10^-15, that I don't want to appear more than once. If they
were identical, I would just use Union[data] and be finished. Is there
a way to set a tollerance for the Union function?
I tried to use SetPrecision to get rid of the unwanted extra digits,
but Union[SetPrecision[data,n]] gives the same result as Union[data].
What exactly does SetPrecision do? It seems that it's not just
dropping the digits beyond the limit I set.
Andre