Negative years with strptime?
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Negative years with strptime?
 
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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 [[alternative HTML version deleted]] ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
Re: Negative years with strptime?
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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 > > [[alternative HTML version deleted]] > > ______________________________________________ > [hidden email] mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
Re: Negative years with strptime?
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?as.Date
Why would pre 0000 years be handled correctly? The help file explicitly states that they likely will not. Note: The default formats follow the rules of the ISO 8601 international standard which expresses a day as ‘"2001-02-03"’. If the date string does not specify the date completely, the returned answer may be system-specific. The most common behaviour is to assume that a missing year, month or day is the current one. If it specifies a date incorrectly, reliable implementations will give an error and the date is reported as ‘NA’. Unfortunately some common implementations (such as ‘glibc’) are unreliable and guess at the intended meaning. Years before 1CE (aka 1AD) will probably not be handled correctly. On Tue, Jul 10, 2012 at 4:59 PM, Rui Barradas <[hidden email]> 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 >> >> [[alternative HTML version deleted]] >> >> ______________________________________________ >> [hidden email] mailing list >> https://stat.ethz.ch/mailman/listinfo/r-devel >> > > ______________________________________________ > [hidden email] mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel -- Jeffrey Ryan [hidden email] www.lemnica.com www.esotericR.com ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
Re: Negative years with strptime?
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In reply to this post by Rui Barradas
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 <[hidden email]> 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 >> >> [[alternative HTML version deleted]] >> >> ______________________________**________________ >> [hidden email] mailing list >> https://stat.ethz.ch/mailman/**listinfo/r-devel<https://stat.ethz.ch/mailman/listinfo/r-devel> >> >> > [[alternative HTML version deleted]] ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
Re: Negative years with strptime?
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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 <[hidden email] > <mailto:[hidden email]>> 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 > > [[alternative HTML version deleted]] > > ________________________________________________ > [hidden email] <mailto:[hidden email]> mailing list > https://stat.ethz.ch/mailman/__listinfo/r-devel > <https://stat.ethz.ch/mailman/listinfo/r-devel> > > > ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel |
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