[R] Still confused about classes
Prof Brian Ripley
ripley at stats.ox.ac.uk
Fri Apr 29 09:04:23 CEST 2011
methods(class = "Date")
would have got you there.
(Date is not an S4 class, so people should not be setting S4 methods
on it without very good reason, and there are none in R itself.)
On Thu, 28 Apr 2011, Joshua Wiley wrote:
> 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")
Call format(), not its methods, or use strftime() directly.
> On Thu, Apr 28, 2011 at 11:05 PM, Russ Abbott <russ.abbott at gmail.com> wrote:
>> 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.
>> 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.
>> *-- Russ *
>> [[alternative HTML version deleted]]
>> R-help at r-project.org mailing list
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
> Joshua Wiley
> Ph.D. Student, Health Psychology
> University of California, Los Angeles
> R-help at r-project.org mailing list
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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