R devel - Aug 1999 - cbind is not generic as claimed, omits labels where S has them (PR#240)

On 5 Aug 1999, Peter Dalgaard BSA wrote:
> (1) The docs are clearly wrong (or perhaps rather, wishful thinking)
Sorry, but always the docs are right and the implementation wrong.
That's an axiom of professional computer programming (so I am told
by several ex-professional computer programmers.)
> (2) Cbind should be generic as in Splus
> 
> (3) For the labels, one needs essentially to implement deparse.level
>     or face the horrors of
>    
eval(substitute(cbind(a,b,deparse.level=2),list(a=rnorm(10),b=rnorm(10))))
Really? Or try a bit less hard?  Getting the common cases right is not
too hard -- ts.union etc seem normally to be about right, and they have
simple code.
> (4) The dataframe special casing seems to be an evasion. The sticky
>     bit is that one needs to dispatch on *any* argument. For Splus (3.4)
>     compatibility, one has to check each argument for its class
>     method, and if all arguments agree - in the sense that all the
>     arguments that have class methods must have the same one, dispatch
>     to that method. If they disagree, print error message and try
>     default method. 
> 
>     Whoever wrote the code seems to have decided that things would be
>     easier if one assumed that the only method for cbind was
>     cbind.data.frame...
> 
>     Note that by the above logic, if you make a cbind.ts, you can't
>     cbind a time series to a data frame!
That's OK, as I can coerce a data frame to a ts, but in general I want to
cbind ts objects with non-trivial time bases.

I don't think documenting what we have is a good way out here....

-- 
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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ripley@stats.ox.ac.uk writes:
> On 5 Aug 1999, Peter Dalgaard BSA wrote:
> 
> > (1) The docs are clearly wrong (or perhaps rather, wishful thinking)
> 
> Sorry, but always the docs are right and the implementation wrong.
> That's an axiom of professional computer programming (so I am told
> by several ex-professional computer programmers.)
Hmm. I think there are counterexamples...
> 
> > (2) Cbind should be generic as in Splus
> > 
> > (3) For the labels, one needs essentially to implement deparse.level
> >     or face the horrors of
> >    
eval(substitute(cbind(a,b,deparse.level=2),list(a=rnorm(10),b=rnorm(10))))
> 
> Really? Or try a bit less hard?  Getting the common cases right is not
> too hard -- ts.union etc seem normally to be about right, and they have
> simple code.
I don't think it's hard to implement deparse.level. The main
difficulty is figuring out who does the deparsing. The generic, the
default, or the specific method? 
> > (4) The dataframe special casing seems to be an evasion. The sticky
> >     bit is that one needs to dispatch on *any* argument. For Splus
(3.4)
> >     compatibility, one has to check each argument for its class
> >     method, and if all arguments agree - in the sense that all the
> >     arguments that have class methods must have the same one, dispatch
> >     to that method. If they disagree, print error message and try
> >     default method. 
> > 
> >     Whoever wrote the code seems to have decided that things would be
> >     easier if one assumed that the only method for cbind was
> >     cbind.data.frame...
> > 
> >     Note that by the above logic, if you make a cbind.ts, you
can't
> >     cbind a time series to a data frame!
> 
> That's OK, as I can coerce a data frame to a ts, but in general I want
to
> cbind ts objects with non-trivial time bases.
> 
> I don't think documenting what we have is a good way out here....
Agreed. But if you want it in 0.65 don't expect me to do it. I'll be
away for the weekend and fly to ISI/Helsinki on Tuesday.

-- 
   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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