For what it's worth, I cannot reproduce this problem under a nearly identical instance of R (R 2.12.1, Win 7 Pro 64-bit). I also can't reproduce the problem with R 2.13.0. You've got something truly weird going on with your particular instance of R.
> is.na(strptime("5/3/1992", format="%m/%d/%Y")) [1] FALSE > is.na(strptime("5/2/1992", format="%m/%d/%Y")) [1] FALSE > sessionInfo() R version 2.12.1 (2010-12-16) Platform: i386-pc-mingw32/i386 (32-bit) locale: [1] LC_COLLATE=English_United States.1252 [2] LC_CTYPE=English_United States.1252 [3] LC_MONETARY=English_United States.1252 [4] 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] rj_0.5.2-1 lattice_0.19-17 loaded via a namespace (and not attached): [1] grid_2.12.1 rJava_0.8-8 tools_2.12.1 On Wed, Jun 22, 2011 at 2:40 PM, Alexander Shenkin <ashen...@ufl.edu> wrote: > On 6/22/2011 1:34 PM, Sarah Goslee wrote: >> On Wed, Jun 22, 2011 at 2:28 PM, David Winsemius <dwinsem...@comcast.net> >> wrote: >>> >>> On Jun 22, 2011, at 2:03 PM, Sarah Goslee wrote: >>> >>>> Hi, >>>> >>>> On Wed, Jun 22, 2011 at 11:40 AM, Alexander Shenkin <ashen...@ufl.edu> >>>> wrote: >>>>>> >>>>>> is.na(strptime("5/2/1992", format="%m/%d/%Y")) >>>>> >>>>> [1] FALSE >>>>>> >>>>>> is.na(strptime("5/3/1992", format="%m/%d/%Y")) >>>>> >>>>> [1] TRUE >>>> >>>> I can't reproduce your problem on R 2.13.0 on linux: >>> >>> I also cannot reproduce it on a Mac with 2.13.0 beta >> >> Which strongly suggests that you should start by upgrading your R >> installation if at all possible. >> >> I'd also recommend trying it on a default R session, with no extra >> packages loaded, and no items in your workspace. It's possible that >> something else is interfering. >> >> On linux, that's achieved by typing R --vanilla at the command line. >> I'm afraid I don't know how to do it for Windows, but should be >> similarly straightforward. >> > Thanks Sarah. Still getting the problem. I should surely upgrade, but > still, not a bad idea to get to the bottom of this, or at least have it > documented as a known issue. BTW, I'm on Windows 7 Pro x64. > > (running Rgui.exe --vanilla): > >> is.na(strptime("5/3/1992", format="%m/%d/%Y")) > [1] TRUE > >> is.na(strptime("5/2/1992", format="%m/%d/%Y")) > [1] FALSE > >> sessionInfo() > R version 2.12.1 (2010-12-16) > Platform: i386-pc-mingw32/i386 (32-bit) > > locale: > [1] LC_COLLATE=English_United States.1252 > [2] LC_CTYPE=English_United States.1252 > [3] LC_MONETARY=English_United States.1252 > [4] LC_NUMERIC=C > [5] LC_TIME=English_United States.1252 > > attached base packages: > [1] stats graphics grDevices utils datasets methods base > > ______________________________________________ > 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. > -- ___________________________ Luke Miller Postdoctoral Researcher Marine Science Center Northeastern University Nahant, MA (781) 581-7370 x318 ______________________________________________ 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.