[R] Why is there error in as.POSIXlt.character when using strftime()?

[C W]

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 <jdnewmil using 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.duncan using 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
> >
> >______________________________________________
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> >and provide commented, minimal, self-contained, reproducible code.
>
> --
> Sent from my phone. Please excuse my brevity.
>

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