[R] day, month, year functions

[Gregor Gorjanc]

Martin Maechler wrote:
>>>>>> "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 !
> 

Pheu, a good catch. You are definitely right!

> - 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.

My proposal above was just a "direction" to a common way of dealing with
dates within R. If as.POSIXlt() methods is the way, that is perfectly
fine with me.

-- 
Lep pozdrav / With regards,
    Gregor Gorjanc

----------------------------------------------------------------------
University of Ljubljana     PhD student
Biotechnical Faculty
Zootechnical Department     URI: http://www.bfro.uni-lj.si/MR/ggorjan
Groblje 3                   mail: gregor.gorjanc <at> bfro.uni-lj.si

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