[R] strptime - %p format doesn't seem to be working

[Prof Brian Ripley]

On Thu, 30 Nov 2006, Edward Abraham wrote:

> Hi there,
>
> Am I missing something? The "%p" format, which should match against
> AM/PM,  seems to be broken in R 2.3.1 running on Windows XP SP2. For
> example, the following fails
>
> > strptime("10AM", "%I%p")
> [1] NA
>
>
> whereas the this works as you would expect, but is ambiguous
> > strptime("10", "%I")
> [1] "2006-11-30 10:00:00"
>
> Does this error reproduce on other machines, or is it something wrong
> with my setup?

My Windows XP, R 2.4.0 in English gives

> strptime("10AM", "%I%p")
[1] "2006-11-30 10:00:00"

So, it is a problem specific to you at least for R 2.4.0 (and the posting 
guide asked you to update before posting).  However, the help both warns 
about this being locale-specific and also

      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.  If it
      specifies a date incorrectly, reliable implementations will give
      an error and the date is reported as 'NA'.

so what you say should work is explicitly documented to not necessarily do 
so.


-- 
Brian D. Ripley,                  ripley at 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