[R] Still confused about classes

[Kenn Konstabel]

The function for getting the year from date  is there in package
lubridate (as well as many other convenient functions to work with
dates).

More generally, finding "all" methods for a given class may be a
little tricky. If "all" means everything you have installed and
currently attached to your search path then methods(class="Date") will
do it (for S3 classes). (but "The functions listed are  those which
_are named like methods_ and may not actually be   methods (known
exceptions are discarded in the code). ") The result depends on which
packages you have loaded: in my currently open R session,
methods("Date") lists 36 "possible methods" but after library(zoo) I
get two more ( "as.yearmon.Date" and "as.yearqtr.Date").

Regards,
Kenn


On Fri, Apr 29, 2011 at 9:05 AM, 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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