On Jul 18, 2011, at 11:21 PM, Edwin Sun wrote:
Hello all,
I am manipulating a large database with 70,000 records. "strptime"
generates
a date variable but R treats some of the values as NA. I attach a
simple
example below.
Cannot duplicate but I'm betting on three words:
daylight savings time
--
David.
I have spent hours on this problem. Any hint would be greatly
appreciated.
Many thanks,
Edwin Sun
# =======start of sample code =============
x <- c("2005-04-02 19:03:00", "2005-04-03 02:00:00", "2005-04-03
14:25:00")
y <- strptime(x, format="%Y-%m-%d %H:%M:%S")
x; y; str(x); str(y)
[1] "2005-04-02 19:03:00" "2005-04-03 02:00:00" "2005-04-03 14:25:00"
[1] "2005-04-02 19:03:00" "2005-04-03 02:00:00" "2005-04-03 14:25:00"
chr [1:3] "2005-04-02 19:03:00" "2005-04-03 02:00:00" ...
POSIXlt[1:3], format: "2005-04-02 19:03:00" "2005-04-03 02:00:00" ...
is.na(y)
[1] FALSE TRUE FALSE
difftime(y[2], y[1], units="mins")
Time difference of NA mins
difftime(y[3], y[1], units="mins")
Time difference of 1102 mins
sessionInfo()
R version 2.13.1 (2011-07-08)
Platform: i386-pc-mingw32/i386 (32-bit)
locale:
[1] LC_COLLATE=English_United States.1252
[2] LC_CTYPE=English_United States.1252
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C
[5] LC_TIME=English_United States.1252
attached base packages:
[1] grDevices datasets splines graphics stats tcltk utils
[8] methods base
other attached packages:
[1] svSocket_0.9-51 TinnR_1.0.3 R2HTML_2.2 Hmisc_3.8-3
[5] survival_2.36-9
loaded via a namespace (and not attached):
[1] cluster_1.14.0 grid_2.13.1 lattice_0.19-30 svMisc_0.9-61
[5] tools_2.13.1
# My computer is 64 bit / Microsoft Window 7; R 2.13.1 (32 bit)
# ======= end of sample code ====================
--
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