Hi The same with me on Windows Most probably an issue of daylight savings time setting.
Sys.timezone() [1] "CET" Regards Petr > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-bounces@r- > project.org] On Behalf Of Pascal Oettli > Sent: Friday, February 01, 2013 9:18 AM > To: Boots > Cc: R Help > Subject: Re: [R] difftime() out by 1 hour > > Hello, > > Here is the result I get using your script: > > > sessionInfo() > R version 2.15.2 (2012-10-26) > Platform: x86_64-suse-linux-gnu (64-bit) > > > [1] "2012-03-31 21:00:00" "2012-04-01 00:00:00" "2012-04-01 03:00:00" > [4] "2012-04-01 06:00:00" > Time differences in hours > [1] 3 3 3 > attr(,"tzone") > [1] "" > [1] "2012-10-06 21:00:00" "2012-10-07 00:00:00" "2012-10-07 03:00:00" > [4] "2012-10-07 06:00:00" > Time differences in hours > [1] 3 3 3 > attr(,"tzone") > [1] "" > > Regards, > Pascal > > > Le 01/02/2013 16:27, Boots a écrit : > > I have a problem with results from difftime being 1 hour different > than expected. 2 examples are given below: > > > > datetime <- matrix(data=rbind(c("2012-03-31 21:00:00", "2012-04-01 > 00:00:00", "2012-04-01 03:00:00", "2012-04-01 06:00:00"), > > c("2012-10-06 21:00:00", "2012-10-07 00:00:00", > > "2012-10-07 03:00:00", "2012-10-07 06:00:00")), ncol=4, nrow=2) > > > > for (row in 1:2) { > > x <- datetime[row,] > > x1=x[1:length(x)-1] > > x2=x[2:length(x)] > > xd=difftime(x2,x1) > > print (x) > > print (xd) > > } > > > > [1] "2012-03-31 21:00:00" "2012-04-01 00:00:00" "2012-04-01 03:00:00" > "2012-04-01 06:00:00" > > Time differences in hours > > [1] 3 4 3 > > attr(,"tzone") > > [1] "" > > [1] "2012-10-06 21:00:00" "2012-10-07 00:00:00" "2012-10-07 03:00:00" > "2012-10-07 06:00:00" > > Time differences in hours > > [1] 3 2 3 > > attr(,"tzone") > > [1] "" > > > > Accurate results would be 3 3 3 (hours) in both cases. > > The problem occurs randomly, but only around midnight. > > All the dates between "2012-04-01 06:00:00" and "2012-10-06 21:00:00" > are fine. > > > > I have seen postings about problems with "POSIXlt" and "POSIXct" > > accuracy because of truncation rather than rounding of floating point > representations. > > The response was that it was expected behaviour. > > > > So my question is this expected behaviour, have I used difftime > > incorrectly, and if not, is there a set of date/time functions and > classes that use integer representation to give more accurate results? > I am new to R and I may well be using the wrong set of functions. > > Garry > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > 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. ______________________________________________ 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.
