[R] Still confused about classes

Joshua Wiley jwiley.psych at gmail.com
Fri Apr 29 08:16:56 CEST 2011

Hi Russ,

One tool that might help could be ?methods and ?showMethods

For example:
## for S3
methods(class = "Date")
## for S4
showMethods(classes = "Date")

regarding getting the actual year, I would use (though there may be
better ways):

format.Date(as.Date("2010-01-01"), format = "%Y")



On Thu, Apr 28, 2011 at 11:05 PM, Russ Abbott <russ.abbott at gmail.com> wrote:
> Hi,
> I'm still confused about how to find out what methods are defined for a
> given class.  For example, I know that
>> today <- Sys.Date()
> will produce an object of type Date. But I'm not sure what I can do with
> Date objects or how I can find out.
>> ?Date
> refers me to the Date documentation page. But it doesn't tell me how, for
> example, to extract the current year from a date object.
> I tried
>> year(today)Error: could not find function "year"
> Is there some other function that does the job? I want a function f such
> that    > f(today)    will return 2011. Perhaps there is no such function.
>  But in general I don't have any confidence that I would know how to find it
> if it existed or that I would know how to assure myself that there was no
> such function.
> Thanks.
> *-- Russ *
>        [[alternative HTML version deleted]]
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Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles

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