Since months have different lengths the difference in months is not well defined but lets define it as the difference between the first of the month of two dates. In that case we can use as.yearmon of the zoo package. It converts to year/months, dropping days, using an internal representation of year + 0 for Jan, year + 1/12 for Feb, year + 2/12 for Mar, etc. so differencing and multiplying by 12 gives the number of months:
> # test data > d1 <- Sys.Date(); d1 [1] "2009-11-02" > d2 <- d1 - 100; d2 [1] "2009-07-25" > library(zoo) > 12 * (as.yearmon(d1) - as.yearmon(d2)) [1] 4 On Mon, Nov 2, 2009 at 6:29 AM, Phil Smith <philipsm...@alumni.albany.edu> wrote: > Hi R Community: > > I want to take the difference in two dates: > > dt2 - dt1. > > But, I want the answer in months between those 2 dates. > > Can you advise me? > > Please respond to: p...@cdc.gov > > Thank you! > Phil Smith > Centers for Disease Control and Prevention > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
