[R] problem with unlist POSIX date at midnight

From: Hanneke Schuurmans <H.Schuurmans_at_geo.uu.nl>
Date: Wed 17 Jan 2007 - 12:50:35 GMT


Dear R-users,

I use unlist of POSIX dates to extract the year, hour etc. With that I can search for files in my database which are in the form 'yyyymmddhh_synops.txt'
However, I get stucked during midnight where unlist just gives NA's. The script is given below; the problem accurs at acc.period[16] (midnight). However when I write out the character, unlist works well. But as.character(acc.period[16]) is not the solution....

> dates=seq(as.Date("2006-03-01"), as.Date("2006-11-01"), "days")
> i=1
> begin=paste(dates[i]-1,"09:00:00")
> end=paste(dates[i],"08:00:00")
> acc.period=seq(as.POSIXct(begin),as.POSIXct(end),"hour")
>
> unlist(strptime(acc.period[15],format="%Y-%m-%d %H:%M:%S"))
  sec min hour mday mon year wday yday isdst     0 0 23 28 1 106 2 58 0
> unlist(strptime(acc.period[16],format="%Y-%m-%d %H:%M:%S"))
  sec min hour mday mon year wday yday isdst    NA NA NA NA NA NA NA NA -1
> unclass(strptime(acc.period[16],format="%Y-%m-%d %H:%M:%S"))
$sec
[1] NA

$min
[1] NA

$hour
[1] NA

$mday
[1] NA

$mon
[1] NA

$year
[1] NA

$wday
[1] NA

$yday
[1] NA

$isdst
[1] -1

>
> a="2006-03-01 00:00:00"
> unlist(strptime(a,format="%Y-%m-%d %H:%M:%S"))
  sec min hour mday mon year wday yday isdst     0 0 0 1 2 106 3 59 0
>
> sessionInfo()

R version 2.4.0 (2006-10-03)
i386-pc-mingw32

locale:
LC_COLLATE=English_United States.1252;LC_CTYPE=English_United States.1252;LC_MONETARY=English_United
States.1252;LC_NUMERIC=C;LC_TIME=English_United States.1252

attached base packages:
[1] "methods" "stats" "graphics" "grDevices" "utils" "datasets" [7] "base"

Thanks in advance!

Hanneke

-- 
---------------------------------------------
ir J.M. (Hanneke) Schuurmans
PhD student Hydrology
Department of Physical Geography
Faculty of Geosciences - Universiteit Utrecht
P.O. Box 80115  3508 TC  Utrecht
T +31 (0)30 2532988  F +31 (0)30 2531145
W www.geo.uu.nl/staff/schuurmans

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Received on Wed Jan 17 23:55:46 2007

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