[R] blues in c

[Prof Brian Ripley]

On 25 Sep 2001, Peter Dalgaard BSA wrote:

> Prof Brian Ripley <ripley at stats.ox.ac.uk> writes:
>
> > On Tue, 25 Sep 2001, Bernie McConnell wrote:
> >
> > > G'Day,
> > >
> > > I'm a little  confused why the c function has the followng effect on
> > > classes - is this a feature ?  My workround [ class(cc) <- c("POSIXt",
> > > "POSIXct") ] seems to do the job.
> >
> > It's a legacy
> >
> > c.POSIXct <- function(..., recursive=FALSE)
> >     structure(c(unlist(lapply(list(...), unclass))),
> > class=c("POSIXt","POSIXct"))
> >
> > does the job.
>
> Speaking of the devil... Is there any reason as.POSIXct shouldn't work
> on numeric data?

Yes, there is no way to know what it means.  Numeric data is not a date!

>
> > as.POSIXct(0)
> Error in as.POSIXct.default(0) : Don't know how to convert `0' to class "POSIXct"
> > structure(0,class=c("POSIXt","POSIXct"))
> [1] "1970-01-01 01:00:00 CET"

Yes, that works, but you need to know the meaning of the numeric vector.


> (Discovered by trying
>
> c.POSIXct <- function(..., recursive=FALSE)
>     as.POSIXct(c(unlist(lapply(list(...), unclass))))
>
> )
> --
>    O__  ---- Peter Dalgaard             Blegdamsvej 3
>   c/ /'_ --- Dept. of Biostatistics     2200 Cph. N
>  (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
> ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
>

-- 
Brian D. Ripley,                  ripley at 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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