[R] Fwd: strptime() problem?

javier garcia - CEBAS rn001 at cebas.csic.es
Tue Aug 17 16:25:12 CEST 2004

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:


 [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?

Thanks all, and best regards,

Javier G.

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