[R] Changing date format

[Frederic Ntirenganya]

Thanks All. Your idea is useful!!!

On Tue, Oct 7, 2014 at 1:01 PM, Jim Lemon <jim at bitwrit.com.au> wrote:

> On Tue, 7 Oct 2014 11:51:34 AM Göran Broström wrote:
> > On 2014-10-07 11:27, Jim Lemon wrote:
> > > On Tue, 7 Oct 2014 10:32:42 AM Frederic Ntirenganya wrote:
> > >> Dear All,
> > >>
> > >> How can I change the format of date of day of the year ? for
> > >
> > > example r
> > >
> > >> (i.e. "17 Apr" rather than "108").
> > >>
> > >> The following is the type of the dataset I have
> > >>
> > >> head(Samaru)
> > >>
> > >>    Year Start End Length
> > >>
> > >> 1 1930   108 288    180
> > >> 2 1931   118 288    170
> > >> 3 1932   115 295    180
> > >> 4 1933   156 294    138
> > >> 5 1934   116 291    175
> > >> 6 1935   134 288    154
> > >
> > > Hi Frederic,
> > > The easiest method I can think of is this:
> > >
> > > Samaru$Start<-format(as.Date(
> > >
> > >   paste(Samaru$Year,"01-01",sep="-"))+Samaru$Start,
> > >   "%b %d")
> > >
> > > Samaru$End<-format(as.Date(
> > >
> > >   paste(Samaru$Year,"01-01",sep="-"))+Samaru$End,
> > >   "%b %d")
> >
> > In the package 'eha' I have a function 'toDate':
> >  > require(eha)
> >  > toDate(1930 + 108/365)
> >
> > [1] "1930-04-19"
> >
> > (Interestingly, we are all wrong; the correct answer seems to be
> > "1930-04-18")
> >
> >  > toDate
> >
> > function (times)
> > {
> >      if (!is.numeric(times))
> >          stop("Argument must be numeric")
> >      times * 365.2425 + as.Date("0000-01-01")
> > }
> >
> > The 'inverse' function is 'toTime'.
> >
> > Sometimes it misses by one day; not very important in my
> applications,
> > but may be otherwise.
> >
> Hi Goran,
> You're correct.
>
>  as.Date("Apr 19 1930","%b %d %Y") -
> + as.Date("Jan 1 1930","%b %d %Y")
> Time difference of 108 days
>
> The t
>
> Samaru$Start<-format(as.Date(
>  paste(Samaru$Year,"01-01",sep="-"))+Samaru$Start-1,"%b %d")
> Samaru$End<-format(as.Date(
>  paste(Samaru$Year,"01-01",sep="-"))+Samaru$End-1, "%b %d")
>
> Jim
>
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>



-- 
Frederic Ntirenganya
Maseno University,
Kenya.
Mobile:(+254)718492836
Email: fredo at aims.ac.za
https://sites.google.com/a/aims.ac.za/fredo/

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