Re: [R] question about date's

From: Peter Dalgaard <p.dalgaard_at_biostat.ku.dk>
Date: Tue 13 Dec 2005 - 02:15:59 EST

Prof Brian Ripley <ripley@stats.ox.ac.uk> writes:

> > %W seems to be what is known as "ISO dates" (week starts on Monday),
> > except that
> >
> >> strftime(as.POSIXlt(as.Date("2005-01-01")), "%U")
> > [1] "00"
> >
> > should be week 53, 2004 according to my printed calendar, and emacs
> > calendar-mode too.
>
> I _did_ say
>
> >> That's nothing like as easy, as it is not well-defined.
>
> The POSIX definition is
>
> %U
> Replaced by the week number of the year as a decimal number [00,53].
> The first Sunday of January is the first day of week 1; days in the
> new year before this are in week 0.
>
> %W
> Replaced by the week number of the year as a decimal number [00,53].
> The first Monday of January is the first day of week 1; days in the
> new year before this are in week 0.
>
> so it is doing what it is documented to do. I'd take POSIX as more
> definitive than Emacs ....

But not more definitive than the ISO standard, I hope. There are probably more that 1e8 calendars printed each year according that one.

The two routines are just not doing the same thing. Calendar-mode goes by the ISO standard, strftime by POSIX definitions. Of course it all depends on what the user actually wanted.

-- 
   O__  ---- Peter Dalgaard             ุster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)                  FAX: (+45) 35327907

______________________________________________
R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Received on Tue Dec 13 02:58:13 2005

This archive was generated by hypermail 2.1.8 : Tue 13 Dec 2005 - 04:30:45 EST