[R] Julian Dates

[Ko-Kang Kevin Wang]

Thanks!  chron() is very useful indeed.

Just out of interest, is it possible to do, say in this case, the number 
of months (or quarters) after January 1986?  i.e. use a different time 
interval?

On Mon, 15 Dec 2003, Gabor Grothendieck wrote:

> What you can do to handle this timezone problem is either to use
> POSIXt with GMT or use chron (which does not use timezones so 
> can't cause problems like this):
> 
> Suppose:
> 
> SLDATX <- c( "1986-01-06", "1986-01-17", "1986-02-02", "1986-02-04",
> ,"1986-02-04", "1986-02-21", "1986-03-06", "1986-03-25",
> ,"1986-04-06", "1986-04-10" )
> 
> # then using POSIXt in the GMT timezone:
> 
> TIMESOLD <- as.numeric( julian( as.POSIXlt( SLDATX, tz="GMT" ),
>   origin = as.POSIXct( "1986-01-01", tz = "GMT" ) ) )
> 
> # or the alternative using chron:
> 
> require(chron)
> TIMESOLD2 <- as.numeric( chron( SLDATX, format="y-m-d", 
>   origin = c( month = 1, day = 1, year = 1986 ) ) )
> 
> all.equal(TIMESOLD,TIMESOLD2)
> 

-- 
Cheers,

Kevin

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----
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