Re: cbind is not generic as claimed, omits labels where S has them (PR#241)

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Subject: Re: cbind is not generic as claimed, omits labels where S has them (PR#241)
ripley@stats.ox.ac.uk
Date: Fri 06 Aug 1999 - 15:50:50 EST


Message-Id: <199908060550.HAA04696@pubhealth.ku.dk>

On Fri, 6 Aug 1999 ihaka@stat.auckland.ac.nz wrote:

> On Fri, Aug 06, 1999 at 12:08:05AM +0200, Peter Dalgaard BSA wrote:
> > Ross Ihaka <ihaka@stat.auckland.ac.nz> writes:
> >
> > I played around with this earlier today. There's nothing special about
> > dataframes, S does the same with any classed object. I.e.
> >
> > class(b)<-"my"
> > cbind.my<-function(...)match.call()
> >
> > cbind(a,b)
> >
> > will dispatch cbind.my
>
> I played some more. I think data frames are special somehow.
>
> S> x <- factor(1:10)
> S> y <- data.frame(1:10)
> > class(x)
> [1] "factor"
> S> class(y)
> [1] "data.frame"
> S> class(cbind(x,y))
> [1] "data.frame"
> S> class(cbind(y,x))
> [1] "data.frame"
>
> They seem to overpower other class arguments too.

Once again, there is a difference between what S documents it does and what
it actually does. The on-line help says:

       Returns a matrix that is pieced together from several
       vectors and/or matrices. The functions cbind and rbind are
       generic (relative to their first argument). In particular,
       there are cbind and rbind methods for classes in the
       Matrix library.

I would settle for that. I think what in part is going is that the
one method, in particular the default method, may use another method.

-- 
Brian D. Ripley,                  ripley@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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