[R] Problems with the sort function!?
p.dalgaard at biostat.ku.dk
Fri Nov 5 15:20:32 CET 2004
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-s
>  -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
 1.118897e-16 -1.101549e-16 1.118897e-16
> sort(diff(x) - 1e-3)
 -1.101549e-16 1.118897e-16 1.118897e-16
> diff(sort(diff(x) - 1e-3)[1:2])
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
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