In your data frames, 'y' is a category and the following comment in the
code makes clear this is deliberate.
if( !is.null(levels(xj)) ) {
all.levs[[j]] <- levels(xj)
facCol[j] <- TRUE # turn categories into factors
} else facCol[j] <- is.factor(xj)
The behaviour is compatible with S apart from the comment in the R help
page. That categories are promoted to factors is consistent with the help
for 'category'.
It is not a bug, but the help page could say what happens for categories.
On Fri, 23 Mar 2007, Lutz Prechelt wrote:
> I am sorry.
> Here is a minimal example:
>
> a=data.frame(x=c(1:3),y=unclass(factor(c(5:7))))
> b=data.frame(x=c(11:13),y=unclass(factor(c(7:9))))
> rbind(a,b)
>
> Lutz Prechelt
>
>
--
Brian D. Ripley, [EMAIL PROTECTED]
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 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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