R devel - Sep 2004 - Glitch involving difftime and data frame

This looks unintentional:
> d <- as.Date("2004-09-07")
> dd <- as.Date("2004-10-04")
> data.frame(d,dd,dd-d)
Error in as.data.frame.default(x[[i]], optional = TRUE) :
        can't coerce difftime into a data.frame
> F <- data.frame(d,dd)
> F$foo <- dd-d
> cbind(F,dd-d)
Error in as.data.frame.default(x[[i]], optional = TRUE) :
        can't coerce difftime into a data.frame

Basically, the issue is that as.data.frame on a classed object expects
to find a method and there isn't any for difftime...


-- 
   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

On 7 Sep 2004, Peter Dalgaard wrote:
> This looks unintentional:
Not so.
> > d <- as.Date("2004-09-07")
> > dd <- as.Date("2004-10-04")
> > data.frame(d,dd,dd-d)
> Error in as.data.frame.default(x[[i]], optional = TRUE) :
>         can't coerce difftime into a data.frame
> > F <- data.frame(d,dd)
> > F$foo <- dd-d
> > cbind(F,dd-d)
> Error in as.data.frame.default(x[[i]], optional = TRUE) :
>         can't coerce difftime into a data.frame
> 
> Basically, the issue is that as.data.frame on a classed object expects
> to find a method and there isn't any for difftime...
Difftime depends crucially on attributes on the vector.  I wasn't 
confident that they would be preserved as needed (and I think I had a 
problem example).  Since then we have fixed a lot of the subsetting 
methods, but even so I am not 100% confident.

-- 
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 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595