On Mon, 10 Nov 2008, Farley, Robert wrote:
I have a time zone problem.
Running the code provided I get the result in UTC, and a lot of warnings
like this:
28: In as.POSIXlt.POSIXct(x, tz) ... : unknwon timezone 'PST'
sunrise.set(34.11583, -118.18719, "2008-11-14")
sunrise sunset
newlon 2008-11-14 14:25:02 2008-11-15 00:49:09
Sys.timezone()
[1] "PST"
The result is equivalent to 06:25:02 16:49:09 {PST = UTC-8}
The "correct" values from another source show 06:25 16:50 which agree to
beyond the accuracy of prediction due to atmospheric uncertainty.
How SHOULD I specify the TZ? I would think that PST is a pretty
"standard" ;-) time zone.
Your thoughts are misinformed: PST8PDT is a name of a standard timezone,
but PST is not. See ?Sys.timezone for fuller details. See also the
posting guide: you failed to tell us your OS, which matters here.
Yes, I steal a lot of code snippets. I justify it by telling myself it
helps me learn R.
Robert Farley
Metro
www.Metro.net
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
On Behalf Of stephen sefick
Sent: Saturday, November 08, 2008 17:09
To: R-help
Subject: Re: [R] maptools sunrise sunset function
Nevermind, when one puts in the proper coordinates in decimal degrees
everything works just fine.
thanks for you patience,
Stephen
On Sat, Nov 8, 2008 at 7:40 PM, stephen sefick <[EMAIL PROTECTED]>
wrote:
##This is a function that I am trying to write to calculate sunrise
and sunset and works "mostly", but returns nonsensical values. What
am I #missing? Thanks in advance.
###remember to include maptools as dependence###
library(maptools)
sunrise.set <- function(lat, long, date, timezone="UTC", num.days=1){
#this needs to be long lat#
lat.long <- matrix(c(long, lat), nrow=1)
day <- as.POSIXct(date, tz=timezone)
sequence <- seq(from=day, length.out=num.days , by="days")
sunrise <- sunriset(lat.long, sequence, direction="sunrise",
POSIXct=TRUE)
sunset <- sunriset(lat.long, sequence, direction="sunset",
POSIXct=TRUE)
ss <- data.frame(sunrise, sunset)
ss <- ss[,-c(1,3)]
colnames(ss)<-c("sunrise", "sunset")
return(ss)
}
#This doesn't make any sense
sunrise.set(33.46, 84.25, "2008-11-08", timezone="EST")
--
Stephen Sefick
Research Scientist
Southeastern Natural Sciences Academy
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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