[R] Still confused about classes

Kenn Konstabel lebatsnok at gmail.com
Fri Apr 29 10:35:02 CEST 2011

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

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").


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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