[R] S3 vs S4 class

[Duncan Murdoch]

On 07/10/2008 10:41 AM, Terry Therneau wrote:
>   
>   
>   A simple example:
>   	temp <- as.Date('2001-10-5')
>   	class(temp)
>   	  "Date"
> 
> How do I tell if "Date" is implemented as an S3 or an S4 class type?
> I tried ?class, but didn't see anything obvious.  Functions like inherit() work
> equally well with both types (which is a good thing).
> 
>   I expect the answer will be obvious - once someone points it out to me.

You could use the isS4 function:

 > temp <- as.Date('2001-10-5')
 > isS4(temp)
[1] FALSE

Duncan Murdoch