[R] problem with unlist POSIX date at midnight

[Hanneke Schuurmans]

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....

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[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
unlist(strptime(acc.period[17],format="%Y-%m-%d %H:%M:%S"))
#  sec   min  hour  mday   mon  year  wday  yday isdst
 #   0     0     1     1     2   106     3    59     0
 
 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

Could someone help?

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