[R] Getting the last day of the month.

[Gabor Grothendieck]

Try this:

library(zoo)
x <- "200212"
as.Date(as.yearmon(paste(x, "01", sep = ""), "%Y%m%d"), frac = 1)



On 5/10/07, Patnaik, Tirthankar <tirthankar.patnaik at citi.com> wrote:
> Hi,
>        Given a date, how do I get the last date of that month? I have
> data in the form YYYYMM, that I've read as a date using
>
> > x$Date <-
> as.Date(ISOdate(substr(x$YearEnd,1,4),substr(x$YearEnd,5,6),1))
>
> But this gives the first day of the month. To get the last day of the
> month, I tried
>
> > as.Date(as.yearmon(x$Date,frac=0))
>
> But I don't get the last day of the month here. (Tried frac=1 too.)
>
> I then add a month to the date, substract one day from the resultant
> date. But this wouldn't work for December.
>
> > x$YearEnd
>  [1] 200203 200303 200403 200503 200603 200603 200312 200503 200603
> 200203 200303
> [12] 200403 200503 200512 200612 200203 200303 200403 200503 200603
> >
> > x$Date <- as.Date(ISOdate(substr(x$YearEnd,1,4),
> + as.integer(substr(x$YearEnd,5,6))+1,
> + 1))-1
> > x$Date
>  [1] "2002-03-31" "2003-03-31" "2004-03-31" "2005-03-31" "2006-03-31"
> "2006-03-31"
>  [7] NA           "2005-03-31" "2006-03-31" "2002-03-31" "2003-03-31"
> "2004-03-31"
> [13] "2005-03-31" NA           NA           "2002-03-31" "2003-03-31"
> "2004-03-31"
> [19] "2005-03-31" "2006-03-31"
>
> So I add a year, and set the month to 1 in a quick function.
>
> > GetEOM <- function(yyyymm=200406){
>        year <- as.integer(substr(yyyymm,1,4))
>        month <- as.integer(substr(yyyymm,5,6))
>        if (month==12){
>                date <- as.Date(ISOdate(year+1,1,1))-1
>        }else{
>                date <- as.Date(ISOdate(year,month+1,1))-1
>        }
>        print(date)
> }
>
> x$Date <- as.vector(sapply(x$YearEnd,GetEOM))
>
> str(x$Date)
>
>
> Is there a simpler way to do this please?
>
>
> TIA and best,
> -Tir
>
> Tirthankar Patnaik
> India Strategy
> Citigroup Investment Research
> +91-22-6631 9887
>
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