[R] Julian Dates

[Uwe Ligges]

Ko-Kang Kevin Wang wrote:
> 
> Hi,
> 
> I'm a bit confused how julian() works.  If I understand right, it returns
> the number of days since the origin.
> 
> I have a vector:
> > SLDATX[1:10]
>  [1] "1986-01-06" "1986-01-17" "1986-02-02" "1986-02-04"
>  [5] "1986-02-04" "1986-02-21" "1986-03-06" "1986-03-25"
>  [9] "1986-04-06" "1986-04-10"
> 
> And when I did:
> > TIMESOLD <- as.numeric(julian(as.POSIXlt(SLDATX),
> +                               origin = as.POSIXct("1986-01-01", "")))
> 
> I got:
> > TIMESOLD[1:10]
>  [1]  5.00000 16.00000 32.00000 34.00000 34.00000 51.00000
>  [7] 64.04167 83.04167 95.04167 99.04167
>
> THe first 6 values from TIMESOLD is obvious, however I'm not sure why I
> got decimals from the 7th value, as my input vector does not have any
> specific "times" after the dates.

That's because of the timezone you are using (winter/summertime).
Look what the difference of 0.04167 really is:  0.04167 * 24 ~ 1
hour.....

Uwe Ligges
 
> Any insights would be greatly appreciated...;-D
> 
> --
> Cheers,
> 
> Kevin
> 
> ---------------------------------------------------------------
> "Try not.  Do, do!  Or do not.  There is no try"
>    Jedi Master Yoda
> 
> ----
> Ko-Kang Kevin Wang, MSc
> SLC STATS 10x Workshop Coordinator
> University of Auckland
> New Zealand
> Homepage: http://www.stat.auckland.ac.nz/~kwan022
> Ph: 373-7599  x88475
> 
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