javier garcia - CEBAS <rn001 <at> cebas.csic.es> writes: : : Hi all; : I've already send a similar e-mail to the list and Prof. Brian Ripley : answered me but my doubts remain unresolved. Thanks for the clarification, : but perhaps I wasn't clear enough in posting my questions. : : I've got a postgres database which I read into R. The first column is : Timestamp with timezone, and my data are already in UTC format. An 'printed' : extract of R character column, resulting from the timestamptz field is: : : raincida$ts: : : [2039] "25/03/2000 22:00:00 UTC" "25/03/2000 23:00:00 UTC" : [2041] "26/03/2000 00:00:00 UTC" "26/03/2000 01:00:00 UTC" : [2043] "26/03/2000 02:00:00 UTC" "26/03/2000 03:00:00 UTC" : [2045] "26/03/2000 04:00:00 UTC" "26/03/2000 05:00:00 UTC" : : #And I need to convert this character column into POSIXct, for eventual work. : #As I can see in the documentation, the process is to use strptime(), what : #creates an object POSIXlt and doesn't allow to specify that the time zone of : #the data is already UTC; followed by as.POSIXct() : : > lluvia.strptime <- strptime(raincida$ts, format="%d/%m/%Y %H:%M:%S") : > lluvia.strptime.POSIXct <- as.POSIXct(lluvia.strptime,tz="GMT") : : A "printed" extract is: : : [2039] "2000-03-25 22:00:00 GMT" "2000-03-25 23:00:00 GMT" : [2041] "2000-03-26 00:00:00 GMT" "2000-03-26 01:00:00 GMT" : [2043] "2000-03-26 03:00:00 GMT" "2000-03-26 03:00:00 GMT" : [2045] "2000-03-26 04:00:00 GMT" "2000-03-26 05:00:00 GMT" : : As we can see, elements [2043] differ. Shouldn't they be similar as the rest : of the other shown elements? I thought this was a bug, but it seems that I've : got and conceptual error.(?). This happens several times in my data, and : produces eventual errors. : : Please, how could I resolved this?
[Sorry if this gets posted twice. I had a problem posting and not sure if the first one ever got sent.] I am in a different time zone, EDT, on Windows XP and can't replicate this but you might try reading the latest R News article on dates and times for some ideas, viz. page 32 of: http://cran.r-project.org/doc/Rnews/Rnews_2004-1.pd In particular, try converting the datetimes to chron and then doing your manipulations in chron or else converting them from chron to POSIXct rather than going through POSIXlt: require(chron) r.asc <- raincida$ts r.chron <- chron(substring(r.asc, 1, 10), substring(r.asc, 12, 19), format = c("d/m/y", "h:m:s")) r.ct <- as.POSIXct(r.chron) format(r.ct, tz="GMT") # display in GMT ______________________________________________ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html