[R] what does this mean in R-1.8.1 release notes?
Peter Dalgaard
p.dalgaard at biostat.ku.dk
Fri Nov 21 15:08:09 CET 2003
"Liaw, Andy" <andy_liaw at merck.com> writes:
> > From: Peter Dalgaard [mailto:p.dalgaard at biostat.ku.dk]
> >
> > John Christie <jc at or.psychology.dal.ca> writes:
> >
> > > what does this mean in R-1.8.1 release notes?
> > >
> > > o median() no longer `works' for odd-length
> > factor variables.
> >
> > The median has always been undefined for factors, but nevertheless
> > median() gave an answer. If the length was even, it would
> > fail since it needed to average non-numeric values. This
> > confused some and the answer you got for in the odd-length
> > case was meaningless anyway (what's the median of three
> > pears, four apples, and two bananas?). So now we check.
>
> Why not just give an error if median is given an unordered factor?
That's what we do and didn't:
if (is.factor(x) || mode(x) != "numeric")
stop("need numeric data")
(also for ordered factors; it is not clear what to do if the median
sits between two levels in that case either.)
--
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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