Re: [R] day, month, year functions

From: Martin Maechler <maechler_at_stat.math.ethz.ch>
Date: Thu 17 Aug 2006 - 18:26:45 EST

>>>>> "Gregor" == Gregor Gorjanc <gregor.gorjanc@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:

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



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