Because data.frame converts it. I don't know what rationale was originally used to justify including that transformation automatically, but I think it is much better this way than having POSIXlt in the data frame. POSIXlt is itself like a little data frame, and having data frames inside of data frames gets confusing. I wish column assignment also did this transformation...
b$date2 <- a # leads to overcomplicated data frame b$date3 <- as.POSIXct(a) # my usual idiom --------------------------------------------------------------------------- Jeff Newmiller The ..... ..... Go Live... DCN:<[email protected]> 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. On January 5, 2015 9:17:45 PM PST, Jinsong Zhao <[email protected]> wrote: >On 2015/1/5 20:51, David Winsemius wrote: >> >> On Jan 5, 2015, at 5:47 PM, Jinsong Zhao wrote: >> >>> On 2015/1/5 17:28, Ben Bolker wrote: >>>> Jinsong Zhao <jszhao <at> yeah.net> writes: >>>> >>>> >>>>> In the following code snippet, >>>>> # >>>>> a <- strptime("121114 0510", "%m%d%y %H%M") >>>>> b <- data.frame(date = a, res = 1:5) >>>>> class(a) >>>>> class(b[1,1]) >>>>> # >>>>> I am wondering why the class of a and b[1,1] are not the same. >>>>> >>>>> How to make the class of a and b[1,1] to be same? >>>> >>>> How about >>>> >>>> a <- as.POSIXct(strptime(...)) >>>> >>>> ? (See ?POSIXct) >>> >>> Thanks a lot. >>> >>> I have used as.POSIXct(...). >> >> You may have "used" it, but you don't show any code. I can think of >several ways you could have _thought_ you "used it" but failed to make >any changes to the underlying objects. For instance you could have >executed this code: >> >> as.POSIXct(a) >> >> Which would produce console output but have no effect on 'a'. >> >> >>> I am wondering why the class of a and b[1,1] are not the same. >> >> We are wondering as well. What did you do? >> >> > >I am very sorry for the misleading of my reply. > >I wanted to say that I have used the as.POSIXct(...) in my code, and it > >give the same output for class(a) and class(b[1,1]), as in the >following >code: > >a <- as.POSIXct(strptime("121114 0510", "%m%d%y %H%M")) >aa <- strptime("121114 0510", "%m%d%y %H%M") >b <- data.frame(date = aa, res = 1:5) > >What I am wondering is why class(aa) is different with class(b[1,1]). > >Best, >Jinsong > >______________________________________________ >[email protected] mailing list -- To UNSUBSCRIBE and more, see >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. ______________________________________________ [email protected] mailing list -- To UNSUBSCRIBE and more, see 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.
