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