R help - Nov 2011 - Adding a year to existing date

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


Thanks in advance

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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

Here is an example that could probably be described as "adding a
year":

dates <- c('2008-01-01','2009-03-02')
tmp <- as.POSIXlt(dates)tmp$year <- tmp$year+1
dates2 <- format(tmp)
> dates
[1] "2008-01-01" "2009-03-02"
> dates2
[1] "2009-01-01" "2010-03-02"

## to begin to understand how it works, give the command
##   unclass(tmp)
## (and read the help pages
##   ?as.POSIXlt
##   ?DateTimeClasses

Another example:

dates <- as.Date(c('2008-01-01','2009-03-02'))
tmp <- as.POSIXlt(dates)
tmp$year <- tmp$year+1
dates2 <- as.Date(tmp)



##   ?as.Date
##   ?Date




-Don


-- 
Don MacQueen

Lawrence Livermore National Laboratory
7000 East Ave., L-627
Livermore, CA 94550
925-423-1062





On 11/16/11 8:33 PM, "arunkumar1111" <akpbond007 at gmail.com>
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
>
>
>Thanks in advance
>
>--
>View this message in context:
>http://r.789695.n4.nabble.com/Adding-a-year-to-existing-date-tp4078930p407
>8930.html
>Sent from the R help mailing list archive at Nabble.com.
>
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