[R] Changing date format

[Frederic Ntirenganya]

Hi Lemon,

I am using the code you sent. It's correct for the leap years.
What I want to do is to have both leap  and no-leap years to have 366 days.
that means the 1st March is day 61 of each year.
This will help me to link it with Instat for climatic data analysis.

On Thu, Oct 9, 2014 at 11:54 AM, Jim Lemon <jim at bitwrit.com.au> wrote:

> On Wed, 8 Oct 2014 04:49:02 PM Frederic Ntirenganya wrote:
> > The idea is that I want the non-leap years to be 366 days instead of
> being
> > 365 days. ie. Each year must have 366 days.
> >
> > for example: in the column Start2, Apr 18 will be Apr 17.
> >
> > > head(Samaru)
> >
> >   Year Start End Length Start2   End2
> > 1 1930   108 288    180 Apr 18 Oct 15
> > 2 1931   118 288    170 Apr 28 Oct 15
> > 3 1932   115 295    180 Apr 24 Oct 21
> > 4 1933   156 294    138 Jun 05 Oct 21
> > 5 1934   116 291    175 Apr 26 Oct 18
> > 6 1935   134 288    154 May 14 Oct 15
> >
> > Is there a way to that in R?
> >
> Hi Frederic,
> That doesn't sound like a good idea to me. Instead of having about
> one quarter of the dates wrong, you will have about three quarters
> wrong. When I check the code I sent you:
>
> 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")
>
> it appears to correct for leap years. If you really want to do it yourself,
> you can get a list of leap years here:
>
> http://kalender-365.de/leap-years.php
>
> I think the simplest way is to correct your Start and End fields before
> doing the calculation:
>
> # create a vector of leap years
> leap_years<-c(1804,1808,1812,1816,1820,1824,1828,...,2400)
> # subtract 1 from Start entries in leap years and
> # equal to or greater than 1 March
> Samaru$Start<-Samaru$Start -
>  (Samaru$Year %in% leap_years & Samaru$Start > 59)
> # same for End
> Samaru$End<-Samaru$End -
>  (Samaru$Year %in% leap_years & Samaru$End > 59)
>
> However, I don't think you have to worry about leap years if you are
> using the code I sent.
>
> Jim
>
>


-- 
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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