Re: [R] date/time arithmetic

From: Parlamis Franklin <fparlamis_at_mac.com>
Date: Thu 01 Dec 2005 - 05:56:57 EST

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]]



R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Thu Dec 01 06:18:44 2005

This archive was generated by hypermail 2.1.8 : Thu 01 Dec 2005 - 09:33:11 EST