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sum with dates

5 messages · Ana, R. Michael Weylandt, Rolf Turner +2 more

Ana
# 
How do I sum 15 years to my dataset?

original dataset
         dates        val
1    2001-01-12    1.2
2    2001-02-12    1.2
3    2001-03-12    1.2

result
         dates        val
1    2016-01-12    1.2
2    2016-02-12    1.2
3    2016-03-12    1.2
R. Michael Weylandt
# 
It depends how your dates are stored, but generally you can just add
365*15 to them. E.g.,

print(x <- Sys.Date())
print(x + 365*15)

So for you,

dataset$dates <- dataset$dates + 365*15

Michael
On Mon, Dec 12, 2011 at 9:39 PM, Ana <rrasterr at gmail.com> wrote:
Rolf Turner
#
On 13/12/11 15:39, Ana wrote:
You mean ``How do I ***add*** 15 years ....''

See the thread starting at

     
http://r.789695.n4.nabble.com/Adding-a-year-to-existing-date-tp4078930p4078930.html

     cheers,

         Rolf Turner
Enrico Schumann
# 
If "adding x years to a date" means "increase the YYYY part of a date by 
x", then it should be easiest to manipulate the character representation 
of your date.

dates <- as.Date(c("2001-01-12","2001-02-12","2001-03-12"))

addYear <- function(d,addyears) {
     Y <- as.numeric(strftime(d, "%Y")) + addyears
     as.Date(paste(Y, strftime(d,"-%m-%d"), sep = ""))
}

## (There are leapyears with more than 365 days.)
dates + 365*15
addYear(dates,15)

That said, you cannot "go one year ahead" from February 29, unless you 
go ahead by 4, 8, 12, ... years (unless the new year is divisible by 100 
but not by 400). One possibility would be to leave such dates as Feb 28.

addYear <- function(d,addyears) {
     Y <- as.numeric(strftime(d, "%Y")) + addyears
     YisLeapyear <- Y%%400==0L | ((Y%%4==0L) & !(Y%%100==0L))
     mdpart <- strftime(d,"-%m-%d")
     mdpart <- ifelse(mdpart == "-02-29" & YisLeapyear,
                      mdpart, "-02-28")
     as.Date(paste(Y, mdpart, sep = ""))

}

dates <- as.Date(c("2001-01-12","2001-02-12","2001-03-12",
                    "1899-02-28","1896-02-29","2000-03-01"))
addYear(dates,4)
addYear(dates,5)
addYear(dates,8)



Regards,
Enrico



Am 13.12.2011 04:17, schrieb R. Michael Weylandt: