What is the recommended class for time of day (independent of calendar
date)?
And what is the recommended way to get the time of day from a POSIXct
object? (Not a string representation, but a computable representation.)
I have looked in the man page for DateTimeClasses, in the Time Series
Analysis Task View and in Spector's Data Manipulation book but haven't
found
these. Clearly I can create my own Time class and hack around with the
internal representation of POSIXct, e.g.
days <- unclass(d)/(24*3600)
days-floor(days)
and write print.Time, `-.Time`, etc. etc. but I expect there is already a
standard class or CRAN package.
-s
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If you want the hours from a POSIXct, here is one way of doing it; you can create a function for doing it:> x <- Sys.time() > x[1] "2009-05-20 12:17:13 EDT"> y <- difftime(x, trunc(x, units='days'), units='hours') > yTime difference of 12.28697 hours> as.numeric(y)[1] 12.28697>It depends on what type of computations you want to do with it. You can leave it as POSIXct and carry out a lot of them. Can you specify what you want? On Wed, May 20, 2009 at 10:57 AM, Stavros Macrakis <macrakis@alum.mit.edu>wrote:> What is the recommended class for time of day (independent of calendar > date)? > > And what is the recommended way to get the time of day from a POSIXct > object? (Not a string representation, but a computable representation.) > > I have looked in the man page for DateTimeClasses, in the Time Series > Analysis Task View and in Spector's Data Manipulation book but haven't > found > these. Clearly I can create my own Time class and hack around with the > internal representation of POSIXct, e.g. > > days <- unclass(d)/(24*3600) > days-floor(days) > > and write print.Time, `-.Time`, etc. etc. but I expect there is already a > standard class or CRAN package. > > -s > > [[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<http://www.r-project.org/posting-guide.html> > and provide commented, minimal, self-contained, reproducible code. >-- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem that you are trying to solve? [[alternative HTML version deleted]]
There is a times class in the chron package. Times are measured in fractions of a day so 1/24 is one hour.> library(chron) > dt <- Sys.time() > tt <- times(format(dt, "%H:%M:%S")) > tt[1] 12:27:46> tt + 1/24[1] 13:27:46 There is an article on dates and times in R News 4/1. On Wed, May 20, 2009 at 10:57 AM, Stavros Macrakis <macrakis at alum.mit.edu> wrote:> What is the recommended class for time of day (independent of calendar > date)? > > And what is the recommended way to get the time of day from a POSIXct > object? (Not a string representation, but a computable representation.) > > I have looked in the man page for DateTimeClasses, in the Time Series > Analysis Task View and in Spector's Data Manipulation book but haven't found > these. Clearly I can create my own Time class and hack around with the > internal representation of POSIXct, e.g. > > ? ?days <- unclass(d)/(24*3600) > ? ?days-floor(days) > > and write print.Time, `-.Time`, etc. etc. but I expect there is already a > standard class or CRAN package. > > ? ? ? ? ? -s > > ? ? ? ?[[alternative HTML version deleted]] > > ______________________________________________ > 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. >