Hello all!!! I want to measure the duration of events (given a start and an end time). The catch is that I require the output in calender days. This means: 02-Jan-2011 00:01:00 minus 01-Jan-2011 23:59:00 should be 1 day (although the real time difference is only 2 minutes) My data is the following head(episode.ct) [1] "2009-07-13 13:37:20 CEST" "2009-07-14 07:29:20 CEST" "2009-07-14 07:51:20 CEST" "2009-07-14 08:45:20 CEST" [5] "2009-07-14 09:43:20 CEST" "2009-07-14 10:01:20 CEST" head(episode.end.ct) [1] "2009-07-13 13:47:20 CEST" "2009-07-14 07:49:20 CEST" "2009-07-14 08:01:20 CEST" "2009-07-14 08:53:20 CEST" [5] "2009-07-14 09:51:20 CEST" "2009-07-14 10:11:20 CEST" attributes(episode.ct) $class [1] "POSIXct" "POSIXt" $tzone [1] "" attributes(episode.end.ct) $class [1] "POSIXct" "POSIXt" $tzone [1] "" When I try :> difftime(episode.ct-episode.end.ct)I get Error in as.POSIXct.default(time1) : do not know how to convert 'time1' to class "POSIXct" Why is that? Is difftime what I need? Thank you very much JT -- View this message in context: http://r.789695.n4.nabble.com/Trouble-Time-Difference-with-difftime-tp3742847p3742847.html Sent from the R help mailing list archive at Nabble.com.
Use Date instead of POSIXct. Since your data is already POSIXct you need to
convert to character and then Date before you use difftime.
> a <- as.POSIXct("2011-08-02 00:01:00")
> b <- as.POSIXct("2011-08-01 23:59:00")
>
as.Date(as.character(a,format="%Y-%m-%d"))-as.Date(as.character(b,format="%Y-%m-%d"))
On 08/14/2011 06:33 AM, Jim Trabas wrote:> Hello all!!!
>
> I want to measure the duration of events (given a start and an end time).
> The catch is that I require the output in calender days. This means:
>
> 02-Jan-2011 00:01:00 minus 01-Jan-2011 23:59:00 should be 1 day (although
> the real time difference is only 2 minutes)
>
>
> My data is the following
>
> head(episode.ct)
> [1] "2009-07-13 13:37:20 CEST" "2009-07-14 07:29:20
CEST" "2009-07-14
> 07:51:20 CEST" "2009-07-14 08:45:20 CEST"
> [5] "2009-07-14 09:43:20 CEST" "2009-07-14 10:01:20
CEST"
>
> head(episode.end.ct)
> [1] "2009-07-13 13:47:20 CEST" "2009-07-14 07:49:20
CEST" "2009-07-14
> 08:01:20 CEST" "2009-07-14 08:53:20 CEST"
> [5] "2009-07-14 09:51:20 CEST" "2009-07-14 10:11:20
CEST"
>
> attributes(episode.ct)
> $class
> [1] "POSIXct" "POSIXt"
>
> $tzone
> [1] ""
>
> attributes(episode.end.ct)
> $class
> [1] "POSIXct" "POSIXt"
>
> $tzone
> [1] ""
>
>
> When I try :
>
>> difftime(episode.ct-episode.end.ct)
> I get
>
> Error in as.POSIXct.default(time1) :
> do not know how to convert 'time1' to class "POSIXct"
>
>
> Why is that? Is difftime what I need?
>
>
> Thank you very much
> JT
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/Trouble-Time-Difference-with-difftime-tp3742847p3742847.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at 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.
You were using difftime incorrectly; look at the help page.> x1 <- as.POSIXct(c('2011-08-11 12:00', '2011-08-14 15:15')) > x1[1] "2011-08-11 12:00:00 EDT" "2011-08-14 15:15:00 EDT"> ceiling(difftime(x1[2], x1[1], units = 'days'))Time difference of 4 days>On Sun, Aug 14, 2011 at 9:33 AM, Jim Trabas <jim.trabas at googlemail.com> wrote:> Hello all!!! > > I want to measure the duration of events (given a start and an end time). > The catch is that I require the output in calender days. This means: > > 02-Jan-2011 00:01:00 ?minus 01-Jan-2011 23:59:00 should be 1 day (although > the real time difference is only 2 minutes) > > > My data is the following > > head(episode.ct) > [1] "2009-07-13 13:37:20 CEST" "2009-07-14 07:29:20 CEST" "2009-07-14 > 07:51:20 CEST" "2009-07-14 08:45:20 CEST" > [5] "2009-07-14 09:43:20 CEST" "2009-07-14 10:01:20 CEST" > > head(episode.end.ct) > [1] "2009-07-13 13:47:20 CEST" "2009-07-14 07:49:20 CEST" "2009-07-14 > 08:01:20 CEST" "2009-07-14 08:53:20 CEST" > [5] "2009-07-14 09:51:20 CEST" "2009-07-14 10:11:20 CEST" > > attributes(episode.ct) > $class > [1] "POSIXct" "POSIXt" > > $tzone > [1] "" > > attributes(episode.end.ct) > $class > [1] "POSIXct" "POSIXt" > > $tzone > [1] "" > > > When I try : > >> difftime(episode.ct-episode.end.ct) > > I get > > Error in as.POSIXct.default(time1) : > ?do not know how to convert 'time1' to class "POSIXct" > > > Why is that? Is difftime what I need? > > > Thank you very much > JT > > -- > View this message in context: http://r.789695.n4.nabble.com/Trouble-Time-Difference-with-difftime-tp3742847p3742847.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help at 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. >-- Jim Holtman Data Munger Guru What is the problem that you are trying to solve?