[Rd] (PR#9578) rbind.data.frame reacts on levels without factor

prechelt at inf.fu-berlin.de prechelt at inf.fu-berlin.de
Thu Mar 29 13:44:49 CEST 2007

Brian wrote:
> In your data frames, 'y' is a category
> The behaviour is compatible with S apart from the comment in=20
> the R help=20
> page.  That categories are promoted to factors is consistent=20
> with the help for 'category'.

I have been around S and R for about 10 years, but had
never heard of categories before.
All information I get about categories via=20
in R 2.4.1 is
  'category' has been an old-S function before there were factors;
  should be replaced by 'factor' throughout!

Maybe it's time to drop this particular backwards compatibility=20
feature from rbind?


> It is not a bug, but the help page could say what happens for=20
> categories.
> On Fri, 23 Mar 2007, Lutz Prechelt wrote:
> > I am sorry.
> > Here is a minimal example:
> >
> > a=3Ddata.frame(x=3Dc(1:3),y=3Dunclass(factor(c(5:7))))
> > b=3Ddata.frame(x=3Dc(11:13),y=3Dunclass(factor(c(7:9))))
> > rbind(a,b)

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