[R] groupe averages error

[Prof Brian Ripley]

> From: "Charles Raux" <Charles.Raux at let.ish-lyon.cnrs.fr>
> To: <r-help at stat.math.ethz.ch>
> Date: Fri, 24 Nov 2000 10:41:29 +0100
> Subject: [R] groupe averages error
 
> I want to get subsets averaged on numeric variables number 5:13 but I 
> get the error below that I cannot understand.
> > is.factor(dat$Statut)
> [1] TRUE
> > s<-ave(dat[,5:13],dat$Statut)
> Error in [<-.data.frame(*tmp*, , value = if (n) { : 
>         Argument "i" is missing, with no default
> 
Nor can I, but then I don't have your data, nor the result of traceback()
(which can be *very* helpful).  However, ave() does not apply to
dataframes, and its help page says

Usage:

     ave(x, ..., FUN = mean)

Arguments:

       x: A numeric.

I think you probably need to use by()

> dat <- as.data.frame(matrix(rnorm(1300), 100)) 
> dat$Statut <- factor((0:99)%/%10)
> by(dat[,5:13],dat$Statut, function(x) sapply(x, mean))

for example.


-- 
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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