[R] Problems with date-format (R 2.1.1 + chron)

[Gabor Grothendieck]

Here are some different approaches to this problem:

#1 just convert it to chron without using Date class.
days(chron("21-07-2005", format = "d-m-y"))

#2 after converting it to Date, convert it to numeric and then
# to chron to avoid the problem
dd <- as.Date("21-07-2005", "%d-%m-%y")
days(chron(unclass(dd)))

#3 do not use chron in the first place, just Date
dd <- as.Date("21-07-2005", "%d-%m-%y")
ordered(format(dd, "%d"), lev = 1:31)

Note that days in the chron package gives the answer as an ordered 
factor, which is what is assumed is desired in these examples as
well as pointers to further information in the references.

R News 4/1 Help Desk has some examples of date manipulations
in Date, chron and POSIXct in the table at the end of the article.

On 7/19/05, Gabor Grothendieck <ggrothendieck at gmail.com> wrote:
> On 7/19/05, Gabor Grothendieck <ggrothendieck at gmail.com> wrote:
> > I think its likely that you are using different versions of chron.
> > I noticed that version "2.2-33" of chron had the statement:
> >
> >   tms <- dts - trunc(dts)
> >
> > but version "2.2-35" seems to have replaced it with:
> >
> >  tms <- dts - floor(dts)
> >
> > and that seems to be causing the problem.
> >
> > As a workaround:
> >
> >    floor.Date <- floor.trunc
> 
> That should have been:
> 
>      floor.Date <- trunc.Date
> 
> >    days(as.Date("21-07-2005", "%d-%m-%y"))
> >
> >
> > On 7/19/05, Carsten Steinhoff <carsten.steinhoff at stud.uni-goettingen.de> wrote:
> > > Hello,
> > >
> > > today I've updated on the newest R-Version. But sadly a function I needed
> > > didnt want to work:
> > > The input is e.g.
> > >
> > > days(as.Date("21-07-2005","%d-%m-%y"))
> > >
> > > the error is: Fehler in Math.Date(dts): floor nicht definiert für Date
> > > Objekte
> > > (Error in Math.Date(dts): floor not defined for date objects)
> > >
> > > Same for year. Only months gives me the correct output.
> > > In Version 2.01 it worked very well, with the same chron library.
> > > Whats wrong ?
> > >
> > > Carsten
> > >
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> > >
> >
>