On Mon, 29 May 2000, RINNER Heinrich wrote:
> Dear R-users!
>
> I am using R 1.0.0 and Windows NT 4.0. I want to compute ranks for the
> values of a variable, in several subgroups of a data.frame.
> Currently I use:
> > #example:
> > x <-
data.frame(group=c("A","A","B","A","B","B","A"),
> val=c(10,3,9,3,5,1,7))
> > x
> group val
> 1 A 10
> 2 A 3
> 3 B 9
> 4 A 3
> 5 B 5
> 6 B 1
> 7 A 7
> > x.new<-x[order(x$group), ]
> > x.new$valgroupranks <- unlist(tapply(x.new$val, x.new$group, rank))
> > x.new
> group val valgroupranks
> 1 A 10 4.0
> 2 A 3 1.5
> 4 A 3 1.5
> 7 A 7 3.0
> 3 B 9 3.0
> 5 B 5 2.0
> 6 B 1 1.0
> >
> This seems to work, but I wonder if there is a more "natural"
(simple?) way
> to do that?
Look at by():
> by(x[2], x$group, rank)
x$group: A
[1] 4.0 1.5 1.5 3.0
------------------------------------------------------------
x$group: B
[1] 3 2 1
> c(by(x[2], x$group, rank), recursive=T)
A1 A2 A3 A4 B1 B2 B3
4.0 1.5 1.5 3.0 3.0 2.0 1.0
--
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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