[R] day, month, year functions

[Martin Maechler]

>>>>> "Gregor" == Gregor Gorjanc <gregor.gorjanc at bfro.uni-lj.si>
>>>>>     on Fri, 11 Aug 2006 00:27:27 +0000 (UTC) writes:

    Gregor> Gabor Grothendieck <ggrothendieck <at> gmail.com> writes:
    >> 
    >> Here are three ways:
    >> 
    >> xx <- as.Date("2006-01-05")
    >> 
    >> # 1. use as.POSIXlt
    >> as.POSIXlt(xx)$mday
    >> as.POSIXlt(xx)$mon + 1
    >> as.POSIXlt(xx)$year + 1900
    >> 
    >> # 2. use format
    >> as.numeric(format(xx, "%d"))
    >> as.numeric(format(xx, "%m"))
    >> as.numeric(format(xx, "%Y"))
    >> 
    >> # 3. use month.day.year in chron package
    >> library(chron)
    >> month.day.year(unclass(xx))$day
    >> month.day.year(unclass(xx))$month
    >> month.day.year(unclass(xx))$year

    Gregor> Hi,

    Gregor> it would really be great if there would be

    Gregor> sec(), min(), hour() day(), month(), year()

    Gregor> generic functions that would work on all "date" classes. Where
    Gregor> applicable of course. I imagine that argument to get out integer
    Gregor> or character would alse be nice.

I disagree pretty strongly:

- We definitely don't want min() to return minutes instead of
  minimum !

- Why pollute the namespace with 6 (well, actualy 5!) new
  function names, when  as.POSIXlt()  
  *REALLY* is there exactly for this purpose ???

I rather think the authors of each of the other old-fashioned
"date" classes should provide as.POSIXlt() methods for their
classes.

Then, we'd have uniform interfaces, following's Gabor's "# 1."
above.

Martin Maechler, ETH Zurich