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

[ripley@stats.ox.ac.uk]

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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