[R] Adding a year to existing date

[Rolf Turner]

On 17/11/11 17:33, arunkumar1111 wrote:
> Hi
>
>   I need to add an year to and date field in the dataframe.
>
> Please help me
>
> X Date
> 1 2008-01-01
> 2 2008-02-01
> 3 2003-03-01

I can't find anything built in.  This is probably because "year" is an 
ill-defined
unit; years vary in length in a somewhat peculiar fashion.  So doing 
arithmetic
with respect to years is frowned on.

However you might try this:

`%+%` <- function(x,y){
if(!isTRUE(all.equal(y,round(y)))) stop("Argument \"y\" must be an 
integer.\n")
  x <- as.POSIXlt(x)
  x$year <- x$year+y
as.Date(x)
}

Then:

xxx <- as.Date(c("2008-01-01","2008-02-01","2003-03-01"))
xxx %+% 1
[1] "2009-01-01" "2009-02-01" "2004-03-01"

Dunno what dangers lurk; caveat utilitor.

     cheers,

         Rolf Turner