On 11/30/05, Parlamis Franklin <[EMAIL PROTECTED]> wrote: > I agree there are workarounds (although reduction to secs is not > necessarily graceful when you want to add, say, "1 month" to a date,
You can do that without difftime via: seq(x, len = 2, by = "month")[2] > or any other increment for which the total number of seconds is not > fixed--and is also complicated by the existence of leap seconds). > But upon inspection, they are never as clean as they seem. > > The representation in the man pages that difftime / date-time > arithmetic was possible made me hopeful that some of these tasks had > been handled already, in a manner consistent with the internal date- > time functions. > > > On Nov 30, 2005, at 9:42 AM, bogdan romocea wrote: > > > What do you need a bunch of functions for? I'm not familiar with the > > details of difftime objects, however an easy way out of here is to get > > the time difference in seconds, which you can then add or subtract as > > you please from date-times. > > > > x<-Sys.time(); y<-Sys.time()+3600 > > diff <- as.numeric(difftime(y,x,units="secs")) > > x; y; diff > > y-diff > > > > > >> -----Original Message----- > >> From: [EMAIL PROTECTED] > >> [mailto:[EMAIL PROTECTED] On Behalf Of > >> Parlamis Franklin > >> Sent: Wednesday, November 30, 2005 1:57 PM > >> To: Parlamis Franklin > >> Cc: [email protected] > >> Subject: Re: [R] date/time arithmetic > >> > >> > >> Hi. Sorry to pester, but I didn't get a reply to this > >> (perhaps owing > >> to Thanksgiving break). This seems to be a case where the R > >> language > >> simply doesn't do what it says it does (i.e., allow addition or > >> subtraction of a difftime object and a date-time object). > >> > >> Am I wrong? I am about to write a bunch of functions (easy, but > >> perhaps redundant) to do this, and I just want to know whether there > >> is a bug here, or whether I am missing something obvious. > >> > >> Thanks. > >> > >> FP > >> > >> On Nov 23, 2005, at 10:02 AM, Parlamis Franklin wrote: > >> > >>> On the help page "DateTimeClasses {base}" it says: > >>> > >>> "One can add or subtract a number of seconds or a difftime object > >>> from a date-time object, but not add two date-time objects." > >>> > >>> However, > >>> > >>>> x<-Sys.time(); y<-Sys.time()+3600 > >>>> diff<-y-x > >>>> x; y; diff > >>> [1] "2005-11-23 19:58:20 GMT" > >>> [1] "2005-11-23 20:58:20 GMT" > >>> Time difference of 1 hours > >>>> y-diff > >>> [1] "2005-11-23 20:58:19 GMT" > >>> Warning message: > >>> Incompatible methods ("-.POSIXt", "Ops.difftime") for "-" > >>> > >>> Do I have the syntax wrong? Or is some conversion of the difftime > >>> object to raw seconds necessary prior to performing arithmetic? > >>> And is the help page wrong? > >>> > >>> Thanks. > >>> > >>> Franklin > >>> > >>> > >>> > >>> > >> > >> > >> [[alternative HTML version deleted]] > >> > >> ______________________________________________ > >> [email protected] mailing list > >> https://stat.ethz.ch/mailman/listinfo/r-help > >> PLEASE do read the posting guide! > >> http://www.R-project.org/posting-guide.html > >> > > ______________________________________________ > [email protected] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html > ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
