The printed view of a difftime object is not necessarily reflective of its internal representation. Also, to avoid unpleasant surprises always use a conversion function with specified units (not "auto") if you want to convert between numeric and difftime. --------------------------------------------------------------------------- Jeff Newmiller The ..... ..... Go Live... DCN:<jdnew...@dcn.davis.ca.us> Basics: ##.#. ##.#. Live Go... Live: OO#.. Dead: OO#.. Playing Research Engineer (Solar/Batteries O.O#. #.O#. with /Software/Embedded Controllers) .OO#. .OO#. rocks...1k --------------------------------------------------------------------------- Sent from my phone. Please excuse my brevity.
Jun Shen <jun.shen...@gmail.com> wrote: >Thanks Jim and David, > >The difftime() is exactly what I am looking for. Just out of curiosity >why >the unit of output is different. here is an example of the dataframe. > >test<-structure(list(SPDTC = c("2012-08-27T09:30", "2012-08-06T10:08", >"2012-08-13T07:41", "2012-07-17T07:50", "2012-09-11T10:29"), > TimeBL = c("2012-07-17T07:50", "2012-07-17T07:50", "2012-07-17T07:50", > "2012-07-17T07:50", "2012-07-17T07:50")), .Names = c("SPDTC", >"TimeBL"), row.names = c(NA, 5L), class = "data.frame") > >Here is the calculation I did originally. > >>with(test,strptime(SPDTC,format='%Y-%m-%dT%H:%M')-strptime(TimeBL,format='%Y-%m-%dT%H:%M')) > >The result is in seconds. > > >On Fri, Aug 9, 2013 at 1:55 PM, David Winsemius ><dwinsem...@comcast.net>wrote: > >> >> On Aug 9, 2013, at 10:37 AM, Jun Shen wrote: >> >> > Hi all, >> > >> > I used strptime() to convert character strings to time and did some >> > subtraction calculation. >> > >> > a<-'2012-07-17T07:50' >> > b<-'2012-08-27T09:30' >> > >> > >strptime(a,format='%Y-%m-%dT%H:%M')-strptime(b,format='%Y-%m-%dT%H:%M') >> > >> > The result shows >> > >> > Time difference of -41.06944 days. >> > >> > However when these operations performed in a dataframe, the time >> difference >> > is in the unit of seconds. Why is that? What I really want is in >hours. I >> > know I can convert the results manually to hours but just wonder if >there >> > is way to control the unit. Thanks. >> >> ?difftime >> ?`-.POSIXt` >> >> Should provide exactly what is requested (and is linked from the >> ?DateTimeClasses help page.) >> >> -- >> David Winsemius >> Alameda, CA, USA >> >> > > [[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.