[R] classes with chron slots

[Gabor Grothendieck]

On 6/23/05, Martin Maechler <maechler at stat.math.ethz.ch> wrote:
> >>>>> "Sebastian" == Sebastian Luque <spluque at gmail.com>
> >>>>>     on Wed, 22 Jun 2005 15:50:50 -0500 writes:
> 
>    Sebastian> I'd like to define a class with a chron slot, but:
>    R> require(chron)
>    R> setClass("myclass", representation(datetime = "chron"))
>    Sebastian> [1] "myclass"
>    Sebastian> Warning message:
>    Sebastian> undefined slot classes in definition of "myclass": datetime(class "chron")
>    Sebastian> in: .completeClassSlots(ClassDef, where)
> 
>    Sebastian> How should such a class be defined?
> 
> You need to first make "chron" into a (pseudo-) S4 class,
> using  setOldClass()
> 
> Then you can extend it or use it as slot class.
> 

Also if you are referring to the chron package then 
the names of the chron classes are 'dates' and 'times' -- not 'chron'.

R> library(chron)
R> example(chron)
...snip...
R> class(dts)
[1] "dates" "times"