as.yearmon converts relative to GMT. If you want something else convert it to character first:
as.yearmon(format(...)) On Thu, Mar 18, 2010 at 2:20 PM, Peter Keller <keller...@gmail.com> wrote: > It looks like a timezone issue, and it's causing confusion to me at least. > > My original data: > gmt <- > c("19880101 0000", "19880101 0100", "19880101 0300", "19880101 0400", > "19880101 0500", "19880101 0600") > > These were converted to local dates/times with > akst<-strptime(gmt,format="%Y%m%d %H%M")-(3600*9) # because I want > local standard, not daylight savings time. > >> dput(akst) > structure(c(567993600, 567997200, 568004400, 568008000, 568011600, > 568015200), class = c("POSIXt", "POSIXct"), tzone = "") > > Which looks like this on my system: >> akst > [1] "1987-12-31 15:00:00 AKST" "1987-12-31 16:00:00 AKST" "1987-12-31 > 18:00:00 AKST" > [4] "1987-12-31 19:00:00 AKST" "1987-12-31 20:00:00 AKST" "1987-12-31 > 21:00:00 AKST" > > but why does this happen? > z<-as.yearmon(akst); z > [1] "Jan 1988" "Jan 1988" "Jan 1988" "Jan 1988" "Jan 1988" "Jan 1988" > > I would expect this: > [1] "Dec 1987" "Dec 1987" "Dec 1987" "Dec 1987" "Dec 1987" "Dec 1987" > > which I can get to by doing this: > z<-as.yearmon(akst-(3600*9)); z > [1] "Dec 1987" "Dec 1987" "Dec 1987" "Dec 1987" "Dec 1987" "Dec 1987" > > But I don't understand why the first one doesn't give the answer I > expect (and would like). > > Thanks for any help- > Peter > >> sessionInfo() > R version 2.10.1 Patched (2010-03-16 r51294) > i386-pc-mingw32 > > locale: > [1] LC_COLLATE=English_United States.1252 LC_CTYPE=English_United > States.1252 > [3] LC_MONETARY=English_United States.1252 LC_NUMERIC=C > [5] LC_TIME=English_United States.1252 > > attached base packages: > [1] stats graphics grDevices utils datasets methods base > > other attached packages: > [1] zoo_1.6-2 > > loaded via a namespace (and not attached): > [1] grid_2.10.1 lattice_0.18-3 tools_2.10.1 > >> Sys.timezone() > [1] "AKDT" > > ______________________________________________ > 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.