Re: [R] Time rather than dates?

From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>
Date: Tue 30 May 2006 - 23:00:51 EST

On Tue, 30 May 2006, Petr Pikal wrote:

> Which version of R do you use?
> Version 2.3.1 beta (2006-05-23 r38179)
>
>> treatment_time<-c("01:02:03","02:03:04")
>> strptime(treatment_time,format="%H:%M:%S")
> [1] "2006-05-30 01:02:03" "2006-05-30 02:03:04"

>From ?strptime

      If the date string does not specify the date completely, the
      returned answer may be system-specific.  The most common behaviour
      is to assume that unspecified seconds, minutes or hours are zero,
      and a missing year, month or day is the current one.

which explains the different answer. Neither of you told us your OS.

>> ttt<-strptime(treatment_time,format="%H:%M:%S")
>
> For changing format of POSIX variables use format
>> format(ttt, "%H:%M")
> [1] "01:02" "02:03"
>
> Maybe also consult locale setting.
>
> HTH
> Petr
>
>
>
> On 30 May 2006 at 14:16, Robert Lundqvist wrote:
>
> To: r-help@stat.math.ethz.ch
> From: Robert Lundqvist <Robert.Lundqvist@ltu.se>
> Date sent: Tue, 30 May 2006 14:16:29 +0200
> Subject: [R] Time rather than dates?
> Send reply to: Robert.Lundqvist@ltu.se
> <mailto:r-help-request@stat.math.ethz.ch?subject=unsubscribe>
> <mailto:r-help-request@stat.math.ethz.ch?subject=subscribe>
>
>> Using strptime() and other functions for dates has been very helpful
>> with the kind of data I often work with. However, I haven't found out
>> how time as such should be specified. All my attempts result in time
>> *and* date:
>>
>>> treatment_time<-c("01:02:03","02:03:04") # hours:minutes:seconds
>>> time.2<-strptime(treatment_time,format="%H:%M:%S")
>>
>>> time.2
>> [1] "1900-01-01 01:02:03" "1900-01-01 02:03:04"
>>
>> Why the 1900-...? I had hoped for some easy conversion from time to
>> numeric data and possibly back. Assistance would be appreciated.
>>
>> Robert

-- 
Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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Received on Tue May 30 23:04:56 2006

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