strptime = string parse time (convert from string to POSIXlt, name of function as specified in POSIX standard)
strftime = string format time (make string, name of function as specified in POSIX standard) as.POSIXlt = convert to POSIX list time format (same as strptime but name fits type conversion function naming pattern in R) as.POSIXct = convert to POSIX continuous time (seconds since epoch, typically 1970-01-01 00:00:00 GMT, useful for computations) ?DateTimeClasses On February 2, 2019 8:51:28 AM PST, C W <tmrs...@gmail.com> wrote: >Thank you all very much, very helpful! :) > >I'm just curious, what does strptime(), strftime(), as.POSIXlt.(), and >as.POSIXct() stand for? > >On Sat, Feb 2, 2019 at 10:41 AM Jeff Newmiller ><jdnew...@dcn.davis.ca.us> >wrote: > >> ... and in general, you need to specify the time zone to avoid >surprises. >> In many cases this can be as simple as >> >> Sys.setenv(TZ="GMT") >> >> but it can be specific to your data set also. >> >> On February 2, 2019 7:09:46 AM PST, Duncan Murdoch < >> murdoch.dun...@gmail.com> wrote: >> >On 01/02/2019 10:45 p.m., C W wrote: >> >> Dear R community, >> >> >> >> I am working with dates. And I get the following error: >> >>> strftime(dat[20], format="%H:%M") >> >> Error in as.POSIXlt.character(as.character(x), ...) : >> >> character string is not in a standard unambiguous format >> > >> >You are using the wrong function: strftime() formats a time object >as >> >a >> >character string. You want strptime() to convert character (or >factor >> >in your case) to a time object. >> > >> >But you need to give the format for the full string, not just the >time >> >at the end. >> > >> >If you really were intending to extract times from dat, then you >need >> >both conversions: >> > >> > > strftime(strptime(dat, format="%m/%d/%y %H:%M"), format = >"%H:%M") >> > [1] "11:32" "11:42" "12:17" "12:31" "12:50" "14:10" "14:19" >"14:59" >> >"15:57" "16:00" "16:46" "16:51" "17:35" "17:59" "18:17" "19:07" >"19:08" >> >[18] "19:31" "21:21" "06:00" "06:20" "06:37" "06:40" "06:46" "07:20" >> >"07:47" "07:50" "07:54" "08:11" "08:23" "08:31" "08:33" "08:43" >"09:04" >> >[35] "09:09" "09:30" "09:59" "10:01" "10:03" "10:05" >> > >> >Duncan Murdoch >> > >> >______________________________________________ >> >R-help@r-project.org 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. >> >> -- >> Sent from my phone. Please excuse my brevity. >> -- Sent from my phone. Please excuse my brevity. ______________________________________________ R-help@r-project.org 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.
