Re: [R] Still confused about classes

From: Russ Abbott <russ.abbott_at_gmail.com>
Date: Fri, 29 Apr 2011 08:15:39 -0700

Thanks, to all. I didn't know about either *methods( ) *or the package * lubridate*, which seems like a very nice *Date *package.

*-- Russ *

On Fri, Apr 29, 2011 at 1:35 AM, Kenn Konstabel <lebatsnok_at_gmail.com> wrote:

> 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]]
> >
> > ______________________________________________
> > R-help_at_r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
>

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