On 29/03/2012 21:05, Steven R Corsi wrote:
That is a good tip. I have tried it and found that it works if I make
sure it was converted to character first. strptime appears to accept
factor variables which is the default when reading in the file originally.
I would say that POSIXct is the way to go if you know the timezone of
the datetimes (it is essential to do the conversion). But you don't
always do so, and then POSIXlt can be useful (although assuming UTC can
also work).
Several times a month we get help requests about times on DST
transitions which shows that people too often think they know the
timezone and in fact do not (as the times are invalid or ambiguous in
the assumed timezone).
as.POSIXct does work with factors ....
z <- "2012-03-29 21:20:05"
> as.POSIXct(z)
[1] "2012-03-29 21:20:05 BST"
> as.POSIXct(factor(z))
[1] "2012-03-29 21:20:05 BST"
Thanks
Steve
On 3/29/2012 2:31 PM, MacQueen, Don wrote:
I also find that POSIXct is generally the most useful, and only use
POSIXlt in special cases.
But have you considered as.POSIXct() instead of strptime()? It works for
me, and I can't remember the last time I had to use strptime() for
converting character to date/time. (But I mostly don't work with multiple
time zones, except for converting to/from UTC.
-Don
______________________________________________
R-help@r-project.org mailing list
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.
--
Brian D. Ripley, rip...@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
______________________________________________
R-help@r-project.org mailing list
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.
