Hello all, After beating my head against the wall for a few hours, I give up. I have two problems. 1. If I use seq() to generate a POSIXct series that crosses a daylight savings to stardard time change I get two values for the first day of change. The time change is Nov 6,2011. The value for Nov 7 turns into 23:00 on Nov 6, thus two values for Nov 6. (see below) So I put a time value (noon) into the sequence, that did give me a correct date sequence.
2. When using that modified date sequence in maptools::sunriset(), on day of change to stardard time the sunrise time is shifted by one hour. (i.e. Nov5 8am, Nov6 6am, Nov7 7am) I can't fathom why sunriset() is giving me funny results on the day of time change. I wonder if there is something amiss with how my windows XP is managing time zones perhaps? I would have expected sunriset() to be using just the day value from its dateTime argument, not the time component? thanks! Michael __________________________ start <- as.POSIXct("2011-11-05") end <- as.POSIXct("2011-11-07") date.ser<-seq(start,end,by='day') # time change is Nov 6,2011 date.ser ##### Two values for Nov 6 as Nov 7th lost an hour. [1] "2011-11-05 00:00:00 PDT" "2011-11-06 00:00:00 PDT" [3] "2011-11-06 23:00:00 PST" ### Add noon to correct flexibility for time shift. start <- as.POSIXct("2011-11-05 12:00:00") end <- as.POSIXct("2011-11-07 12:00:00") date.ser<-seq(start,end,by='day') date.ser [1] "2011-11-05 12:00:00 PDT" "2011-11-06 11:00:00 PST" [3] "2011-11-07 11:00:00 PST" library(maptools) nanaimo <- matrix(c(-123+(-57/60),49+11/60), nrow=1) sunriset(nanaimo, date.ser, direction="sunrise", POSIXct.out=T)[,2] [1] "2011-11-05 08:09:42 PDT" "2011-11-06 06:11:19 PST" [3] "2011-11-07 07:12:56 PST" _______________________________________________________ Michael Folkes Salmon Stock Assessment Canadian Dept. of Fisheries & Oceans Pacific Biological Station 3190 Hammond Bay Rd. Nanaimo, B.C., Canada V9T-6N7 Ph (250) 756-7264 Fax (250) 756-7053 michael.fol...@dfo-mpo.gc.ca [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.