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

[Janko Thyson]

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"))# [1] "2015-52" "2015-53" "2016-53" "2016-01"
ywd <- sprintf("%s-1", yw)(as.POSIXct(ywd, format = "%Y-%V-%u"))# [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]]