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.> ?Daterefers 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]]
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")
HTH,
Josh
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]]
>
> ______________________________________________
> 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.
>
--
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/
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.
>