Message-ID: <x2y8hgnzrj.fsf@biostat.ku.dk>
Date: 2004-11-05T14:20:32Z
From: Peter Dalgaard
Subject: Problems with the sort function!?
In-Reply-To: <permail-2004110513482214681-pilzkabz@ruhr-uni-bochum.de>
Kay Pilz <Kay.Pilz at ruhr-uni-bochum.de> writes:
> Hello All.
>
> I am running R 2.0.0 with a Win XP operating system. The same problem occured
> with R 1.9.1 but not with R.1.3.1 on a Win NT computer.
>
> My request is about the following problem with the sort function:
...
> Taking the difference of the first two entries yields
>
> > s[1]-s[2]
> [1] -2.220446e-16
>
> which seems to be a numerical artefact.
>
> Is this a bug, or just a handling error by me?
You, I think. Consider for instance
> x <- c(1.313,1.314,1.315,1.316)
> diff(x) - 1e-3
[1] 1.118897e-16 -1.101549e-16 1.118897e-16
> sort(diff(x) - 1e-3)
[1] -1.101549e-16 1.118897e-16 1.118897e-16
> diff(sort(diff(x) - 1e-3)[1:2])
[1] 2.220446e-16
--
O__ ---- Peter Dalgaard Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics 2200 Cph. N
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907