[R] how to shift a chron timestamp by 6:30 hours

[Gabor Grothendieck]

On Thu, Jul 28, 2011 at 9:37 AM, Maciej Hoffman-Wecker
<Maciej.Hoffman-Wecker at bioskin.de> wrote:
> Dear help list,
>
> I have a timestamp in as a chron object:
>
>> (x <- chron(dates = c("12/02/11", "22/11/11"),
> +             times = c("07:30:00", "04:00:00"),
> +             format = c(dates = "d/m/y", times = "h:m:s")))
> [1] (12/02/11 07:30:00) (22/11/11 04:00:00)
>
> Now I want to shift the timestamp by 06:30 (hh:mm) backwards, to get
>
> [1] (12/02/11 01:30:00) (21/11/11 21:30:00)
>

Try this:

 x - as.numeric(times("06:30:00"))

If you actually wanted 6 hours behind, which is what the desired
result shown in the post implies, then use "06:00:00" instead.

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