R help - Jul 2010 - help with Date class

I am trying to work with the Date class which is written in S3 and I would
like to access to the elements of the class (for example the year). I've
tryed to do it for example like this:

as.Date(Sys.time)->w
w$year #Doesn't work
w["year"] #is NA

I would like to know the correct way to acces to this value.

Thank you so much

-- 
Elisenda Vila

	[[alternative HTML version deleted]]

On Jul 7, 2010, at 7:25 AM, Elisenda Vila wrote:
> I am trying to work with the Date class which is written in S3 and I  
> would
> like to access to the elements of the class (for example the year).  
> I've
> tryed to do it for example like this:
>
> as.Date(Sys.time)->w
Throws an error  ... since Sys.time is a function
> w$year #Doesn't work
Why should it? Dates are not stored as lists.

?Date
> w["year"] #is NA
>
> I would like to know the correct way to acces to this value.
as.Date(Sys.time)->w
Error in as.Date.default(Sys.time) :
   do not know how to convert 'Sys.time' to class "Date"
 > as.Date(Sys.time())->w
 > w
[1] "2010-07-07"
 > format(w, "%Y")
[1] "2010"

-- 
David Winsemius, MD
West Hartford, CT

On Wed, Jul 07, 2010 at 01:25:43PM +0200, Elisenda Vila
wrote:
> I am trying to work with the Date class which is written in S3 and I would
> like to access to the elements of the class (for example the year).
I've
> tryed to do it for example like this:
> 
> as.Date(Sys.time)->w
w <- Sys.Date()   # does the same, but in one step
> w$year #Doesn't work
> w["year"] #is NA
> 
> I would like to know the correct way to acces to this value.
wp <- as.POSIXlt(w)    # POSIXlt has the components
unclass(wp)            # shows you all components
wp$year + 1900         # stored as year - 1900, see Unix manuals
wp$mon + 1             # stores as mon -1, see Unix manuals


Arguably, extractor functions would be of help here.

-- 
  Regards, Dirk