Re: cbind is not generic as claimed, omits labels where S has them (PR#239)

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Subject: Re: cbind is not generic as claimed, omits labels where S has them (PR#239)
From: Peter Dalgaard BSA (p.dalgaard@biostat.ku.dk)
Date: Fri 06 Aug 1999 - 17:42:23 EST


Message-ID: <x2u2qd8ie8.fsf@blueberry.kubism.ku.dk>

Ross Ihaka <ihaka@stat.auckland.ac.nz> writes:

> 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.

This is because there's no cbind.factor:

S> cbind.factor<-function(...) match.call()
S> cbind(x,y)
      x y
X1.10 1 numeric, 10
attr(, "names"):
[1] "" "X1.10"
Warning messages:
1: Incompatible methods ("cbind.factor", "cbind.data.frame") for "cbind"
2: Number of rows of result is not a multiple of vector length (arg 1) in: cbin
        d(x, y)

(and cbind.data.frame just calls data.frame(...) so it's little wonder
that the result is always a data frame)

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)             FAX: (+45) 35327907
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