[R] Match ISO 8601 week-of-year numbers to month-of-year numbers on Windows with German locale

[Janko Thyson]

Hi David,

thanks for replying and sorry about the HTML/non-plain-text email (I
forgot to change that, shouldn't have happened).

Might just be me, but reading "The documentation for R datetime format
parameters ?strptime says %V is ignored on input." in the
documentation doesn't really tell me all that much. As a user, I would
read that, not completely understand what this means and thus try to
understand it better by applying it in actual code:

(yw <- format(posix, "%Y-%V"))
> # [1] "2015-52" "2015-53" "2016-53" "2016-01"

Which, after checking back with a calendar, would give me reason to
believe that it using %V does in fact seem to work: it's an input to
`format()` and R doesn't seem to ignore it as the correct week numbers
(following ISO 8601) are returned.

Not wanting to stress this particular aspect any further, though, I
would slightly rephrase my original question: is it possible to use
the ISO 8601 convention for weeknumbers at all (on Windows, using a
German locale setting) and if so, how would I link ISO 8601
weeknumbers to the correct month of the year?

Thanks for help,
Janko

On Thu, Jan 12, 2017 at 8:37 PM, David Winsemius <dwinsemius at comcast.net> wrote:
>
>> On Jan 12, 2017, at 8:14 AM, Janko Thyson <janko.thyson at gmail.com> wrote:
>>
>> Dear list,
>>
>> I'm experiencing problems with converting strings of the format
>> "YYYY-<weekofyear>" (e.g. 2016-01, 2016-52) to proper POSIX dates which (I
>> think) I need in order to retrieve the month-of-the-year number.
>>
>> Simpler put: I'd like to match week-of-the-year numbers to
>> month-of-the-year numbers. Ideally, the week-of-the-year number would
>> follow the ISO 8601 convention (i.e. format argument "%V") instead of the
>> US (format argument "%U") or UK (format argument "%W") convention.
>>
>> After posting this to Stackoverflow, I have strong reasons to believe that
>> the issue is caused by Windows:
>> http://stackoverflow.com/questions/41616407/match-iso-8601-week-numbers-to-month-of-year-on-windows-with-german-locale/41617215?noredirect=1#comment70436768_41617215
>>
>> Example:
>>
>> # ISO 8601 convention:
>>
>> (yw <- format(posix, "%Y-%V"))
>
> The documentation for R datetime format parameters ?strptime says %V is ignored on input.
>
>
>> # [1] "2015-52" "2015-53" "2016-53" "2016-01"
>> ywd <- sprintf("%s-1", yw)(as.POSIXct(ywd, format = "%Y-%V-%u"))
>
> The documentation for R datetime format parameters ( = ?strptime) says %V is ignored on input.
>
> You should leartn to post plain text to r-help.
>
> --
> David.
>
>
>> # [1]
>> "2015-01-12 CET" "2015-01-12 CET" "2016-01-12 CET" "2016-01-12 CET"#
>> -> utterly wrong!!!
>>
>> # US convention:
>> (yw <- format(posix, "%Y-%U"))# [1] "2015-51" "2015-52" "2016-00" "2016-01"
>> ywd <- sprintf("%s-1", yw)(as.POSIXct(ywd, format = "%Y-%U-%u"))# [1]
>> "2015-12-21 CET" "2015-12-28 CET" NA               "2016-01-04 CET"#
>> -> NA problem for week 00A fellow R user tested this on both macOS and
>> Ubuntu and he didn't encounter the issue:
>>
>> some_dates <- as.POSIXct(c("2015-12-24", "2015-12-31", "2016-01-01",
>> "2016-01-08"))
>> (year_week <- format(some_dates, "%Y %U"))## [1] "2015 51" "2015 52"
>> "2016 00" "2016 01"
>> (year_week_day <- sprintf("%s 1", year_week))## [1] "2015 51 1" "2015
>> 52 1" "2016 00 1" "2016 01 1"
>> (as.POSIXct(year_week_day, format = "%Y %U %u"))## [1] "2015-12-21
>> EST" "2015-12-28 EST" "2016-01-04 EST" "2016-01-04 EST"
>>
>> My session info:
>>
>>> sessionInfo()
>> R version 3.3.2 (2016-10-31)
>> Platform: x86_64-w64-mingw32/x64 (64-bit)
>> Running under: Windows >= 8 x64 (build 9200)
>>
>> locale:[1] LC_COLLATE=German_Germany.1252
>> LC_CTYPE=German_Germany.1252       LC_MONETARY=German_Germany.1252
>> [4] LC_NUMERIC=C                       LC_TIME=English_United
>> States.1252
>>
>> attached base packages:[1] stats     graphics  grDevices utils
>> datasets  methods   base
>>
>> other attached packages:
>> [1] fva_0.1.0       digest_0.6.10   readxl_0.1.1    dplyr_0.5.0
>> plyr_1.8.4      magrittr_1.5
>> [7] memoise_1.0.0   testthat_1.0.2  roxygen2_5.0.1  devtools_1.12.0
>>
>> loaded via a namespace (and not attached):
>> [1] Rcpp_0.12.8     lubridate_1.6.0 assertthat_0.1  packrat_0.4.8-1
>> crayon_1.3.2    withr_1.0.2
>> [7] R6_2.2.0        DBI_0.5-1       stringi_1.1.2   rstudioapi_0.6
>> tools_3.3.2     stringr_1.1.0  [13] tibble_1.2
>>
>> Any idea on how to workaround this issue on Windows?
>>
>> Thanks and best regards,
>>
>> Janko Thyson
>>
>>       [[alternative HTML version deleted]]
>>
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>
> David Winsemius
> Alameda, CA, USA
>