On my earlier post I forgot to mention the sessionInfo()
R version 2.15.0 (2012-03-30)
Platform: i386-pc-mingw32/i386 (32-bit)
locale:
[1] LC_COLLATE=Portuguese_Portugal.1252
LC_CTYPE=Portuguese_Portugal.1252
[3] LC_MONETARY=Portuguese_Portugal.1252 LC_NUMERIC=C
[5] LC_TIME=Portuguese_Portugal.1252
attached base packages:
[1] stats graphics grDevices utils datasets methods base
Rui Barradas
Em 11-07-2012 02:05, Winston Chang escreveu:
It looks different on my system (Mac, R 2.15.1)
seq(as.Date("0000-01-01"), length = 22, by = "-1 year")
[1] "0000-01-01" "-001-01-01" "-002-01-01" "-003-01-01" "-004-01-01"
[6] "-005-01-01" "-006-01-01" "-007-01-01" "-008-01-01" "-009-01-01"
[11] "-010-01-01" "-011-01-01" "-012-01-01" "-013-01-01" "-014-01-01"
[16] "-015-01-01" "-016-01-01" "-017-01-01" "-018-01-01" "-019-01-01"
[21] "-020-01-01" "-021-01-01"
So in addition to the issues with converting a negative-year string to a
Date, it looks like converting a negative date to a string with
as.character.Date() is probably also not consistent.
It certainly would be useful to have a way of handling dates with
negative years.
-Winston
On Tue, Jul 10, 2012 at 4:59 PM, Rui Barradas <ruipbarra...@sapo.pt
<mailto:ruipbarra...@sapo.pt>> wrote:
Hello,
Is there a bug with negative dates? Just see:
seq(as.Date("0000-01-01"), length = 22, by = "-1 year")
[1] "0000-01-01" "000/-01-01" "000.-01-01" "000--01-01" "000,-01-01"
[6] "000+-01-01" "000*-01-01" "000)-01-01" "000(-01-01" "000'-01-01"
[11] "00/0-01-01" "00//-01-01" "00/.-01-01" "00/--01-01" "00/,-01-01"
[16] "00/+-01-01" "00/*-01-01" "00/)-01-01" "00/(-01-01" "00/'-01-01"
[21] "00.0-01-01" "00./-01-01"
See the year number: "after" the zero, i.e., downward from zero, the
printed character is '/' which happens to be the ascii character
before '0', and before it's '.', etc. This sequence gives the nine
ascii characters before zero as last digit of the year, then the
10th is '0' as (now) expected, then goes to the second digit, etc.
It seems to stop at the first 9, or else we would have some sort of
real problem.
Anyway, this doesn't look right.
Rui Barradas
Em 10-07-2012 22:17, Winston Chang escreveu:
Is there a way to make as.Date() and strptime() process strings with
negative years? It appears that Date objects can contain
negative years and
you can convert them to strings, but you can't convert them back
to Date
objects.
x <- as.Date(c("0001-01-24", "0500-01-24"))
as.character(x)
# "0001-01-24" "0500-02-02"
as.Date(as.character(x))
# "0001-01-24" "0500-01-24"
# Minus 391 days gives negative year
as.character(x - 391)
# "-001-12-30" "0498-12-29"
# Can't convert this string back to Date
as.Date(as.character(x - 391))
# Error during wrapup: character string is not in a standard
unambiguous
format
# as.Date.character uses strptime, so we can try using strptime
directly
strptime(as.character(x), "%Y-%m-%d")
# "0001-01-24" "0500-01-24"
strptime(as.character(x - 391), "%Y-%m-%d")
# NA "0498-12-29"
Thanks,
-Winston
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