On Sep 13, 2010, at 11:56 AM, Andrew Yee wrote:
I'm trying to understand why as.Date() is converting a the modified
date of
a file from August 22 to August 23.
foo <- file.info(file.to.process)
str(foo)
'data.frame': 1 obs. of 10 variables:
$ size : num 5.37e+09
$ isdir : logi FALSE
$ mode :Class 'octmode' int 436
$ mtime : POSIXct, format: "2010-08-22 23:14:52"
$ ctime : POSIXct, format: "2010-09-13 11:34:31"
$ atime : POSIXct, format: "2010-09-09 15:42:00"
$ uid : int 503
$ gid : int 503
$ uname : chr "ayee"
$ grname: chr "ayee"
as.Date(foo$mtime)
[1] "2010-08-23"
In this case as.Date(foo$mtime) gives August 23. I would have
expected
August 22.
You are pretty close to midnight. Probably a TZ issue. Check your
locale settings versus UTC/GMT.
> dt <- as.POSIXct("2010-08-22 23:14:52")
> as.Date(dt)
[1] "2010-08-23"
Happens to me too, but when its 23:14 here, (US-EDT) it's the next day
in Greenwich. The help page says:
"The last [POSIXct] is converted to days by ignoring the time after
midnight in the representation of the time in UTC." That is not
entirely clear to my reading, but I am forced to conclude that it
means as.Date returns the Date in UTC terms rather than in local terms.
--
David.
Thanks,
Andrew
sessionInfo()
R version 2.11.1 Patched (2010-09-11 r52901)
Platform: x86_64-unknown-linux-gnu (64-bit)
locale:
[1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C
[3] LC_TIME=en_US.UTF-8 LC_COLLATE=en_US.UTF-8
[5] LC_MONETARY=C LC_MESSAGES=en_US.UTF-8
[7] LC_PAPER=en_US.UTF-8 LC_NAME=C
[9] LC_ADDRESS=C LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
attached base packages:
[1] stats graphics grDevices utils datasets methods base
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David Winsemius, MD
West Hartford, CT
______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
