[R] strptime, date and conversion of week number into POSIX

[PIKAL Petr]

Hallo Patrick

I found quite usefull for working with weeks package ISOweek

https://cran.r-project.org/web/packages/ISOweek/index.html

Cheers.
Petr
> -----Original Message-----
> From: R-help <r-help-bounces using r-project.org> On Behalf Of Patrick
> Giraudoux
> Sent: Monday, February 22, 2021 5:24 PM
> To: Uwe Ligges <ligges using statistik.tu-dortmund.de>; R mailing list <r-help using r-
> project.org>; Bert Gunter <bgunter.4567 using gmail.com>
> Subject: Re: [R] strptime, date and conversion of week number into POSIX
> 
> Thanks Uwe and  Bert,
> I got the essential now, and can manage. Date handling stays quite a
> challenge with a variable number of weeks in a year, but I can understand
> why. Means eye-control (or NA detection) of strptime conversion stays
> necessary...
> Best,
> Patrick
> 
> 
> Le 22/02/2021 à 17:09, Uwe Ligges a écrit :
> > That monday does not exist. FOr the week before:
> >
> > strptime(paste0("2020-52","-1"),format="%Y-%W-%u")
> > [1] "2020-12-28"
> >
> > One week later is no longer in 2020, so there is no 53th week.
> >
> > Best,
> > Uwe Ligges
> >
> >
> >
> >
> >
> > On 22.02.2021 16:15, Patrick Giraudoux wrote:
> >> Sorry to answer to myself, but the format was clearly incorrect in
> >> the previous post. It should read, refering to the 1th day of the week:
> >>
> >> strptime(paste0(mydate,"-1"),format="%Y-%W-%u")
> >>
> >> It converts better, but with a NA on week 53
> >>
> >>> strptime(paste0(pays$year_week,"-1"),format="%Y-%W-%u")
> >>    [1] "2020-01-06 CET"  "2020-01-13 CET"  "2020-01-20 CET"
> >> "2020-01-27 CET"
> >>    [5] "2020-02-03 CET"  "2020-02-10 CET"  "2020-02-17 CET"
> >> "2020-02-24 CET"
> >>    [9] "2020-03-02 CET"  "2020-03-09 CET"  "2020-03-16 CET"
> >> "2020-03-23 CET"
> >> [13] "2020-03-30 CEST" "2020-04-06 CEST" "2020-04-13 CEST"
> >> "2020-04-20 CEST"
> >> [17] "2020-04-27 CEST" "2020-05-04 CEST" "2020-05-11 CEST"
> >> "2020-05-18 CEST"
> >> [21] "2020-05-25 CEST" "2020-06-01 CEST" "2020-06-08 CEST"
> >> "2020-06-15 CEST"
> >> [25] "2020-06-22 CEST" "2020-06-29 CEST" "2020-07-06 CEST"
> >> "2020-07-13 CEST"
> >> [29] "2020-07-20 CEST" "2020-07-27 CEST" "2020-08-03 CEST"
> >> "2020-08-10 CEST"
> >> [33] "2020-08-17 CEST" "2020-08-24 CEST" "2020-08-31 CEST"
> >> "2020-09-07 CEST"
> >> [37] "2020-09-14 CEST" "2020-09-21 CEST" "2020-09-28 CEST"
> >> "2020-10-05 CEST"
> >> [41] "2020-10-12 CEST" "2020-10-19 CEST" "2020-10-26 CET" "2020-11-02
> >> CET"
> >> [45] "2020-11-09 CET"  "2020-11-16 CET"  "2020-11-23 CET" "2020-11-30
> >> CET"
> >> [49] "2020-12-07 CET"  "2020-12-14 CET"  "2020-12-21 CET" "2020-12-28
> >> CET"
> >> [53] NA                "2021-01-04 CET"  "2021-01-11 CET" "2021-01-18
> >> CET"
> >> [57] "2021-01-25 CET"  "2021-02-01 CET"  "2021-02-08 CET"
> >> Warning message:
> >> In strptime(paste0(pays$year_week, "-1"), format = "%Y-%W-%u") :
> >>     (0-based) yday 369 in year 2020 is invalid
> >>
> >>
> >> Any idea on how to handle this ?
> >>
> >>
> >>
> >>
> >> Le 22/02/2021 à 15:26, Patrick Giraudoux a écrit :
> >>>
> >>> Dear all,
> >>>
> >>> I have a trouble trying to convert dates  given in character to POSIX.
> >>> The date is expressed as a year then the week number e.g. "2020-01"
> >>> (first week of 2020). I thought is can be converted as following:
> >>>
> >>> strptime(mydate,format="%Y-%W")
> >>>
> >>> %W refering to the week of the year as decimal number (00–53) using
> >>> Monday as the first day of week (and typically with the first Monday
> >>> of the year as day 1 of week 1), as indicated in the doc.
> >>>
> >>> However, I got this result, with the month fixed to 02 (february)
> >>> and day 22 (only the year is  converted correctly):
> >>>
> >>> strptime(mydate,format="%Y-%W") [1] "2020-02-22 CET" "2020-02-22
> CET"
> >>> "2020-02-22 CET" "2020-02-22 CET" [5] "2020-02-22 CET" "2020-02-22
> >>> CET" "2020-02-22 CET" "2020-02-22 CET" [9] "2020-02-22 CET"
> >>> "2020-02-22 CET" "2020-02-22 CET" "2020-02-22 CET" [13] "2020-02-22
> >>> CET" "2020-02-22 CET" "2020-02-22 CET" "2020-02-22 CET" [17]
> >>> "2020-02-22 CET" "2020-02-22 CET" "2020-02-22 CET" "2020-02-22 CET"
> >>> [21] "2020-02-22 CET" "2020-02-22 CET" "2020-02-22 CET" "2020-02-22
> >>> CET" [25] "2020-02-22 CET" "2020-02-22 CET" "2020-02-22 CET"
> >>> "2020-02-22 CET" [29] "2020-02-22 CET" "2020-02-22 CET" "2020-02-22
> >>> CET" "2020-02-22 CET" [33] "2020-02-22 CET" "2020-02-22 CET"
> >>> "2020-02-22 CET" "2020-02-22 CET" [37] "2020-02-22 CET" "2020-02-22
> >>> CET" "2020-02-22 CET" "2020-02-22 CET" [41] "2020-02-22 CET"
> >>> "2020-02-22 CET" "2020-02-22 CET" "2020-02-22 CET" [45] "2020-02-22
> >>> CET" "2020-02-22 CET" "2020-02-22 CET" "2020-02-22 CET" [49]
> >>> "2020-02-22 CET" "2020-02-22 CET" "2020-02-22 CET" "2020-02-22 CET"
> >>> [53] "2020-02-22 CET" "2021-02-22 CET" "2021-02-22 CET" "2021-02-22
> >>> CET" [57] "2021-02-22 CET" "2021-02-22 CET" "2021-02-22 CET"
> >>>
> >>> You'll find below a dump of "mydate" you can copy and paster if you
> >>> need a try
> >>>
> >>> Any hint welcome...
> >>>
> >>> Best,
> >>>
> >>> Patrick
> >>>
> >>> mydate <-
> >>> c("2020-01", "2020-02", "2020-03", "2020-04", "2020-05", "2020-06",
> >>> "2020-07", "2020-08", "2020-09", "2020-10", "2020-11", "2020-12",
> >>> "2020-13", "2020-14", "2020-15", "2020-16", "2020-17", "2020-18",
> >>> "2020-19", "2020-20", "2020-21", "2020-22", "2020-23", "2020-24",
> >>> "2020-25", "2020-26", "2020-27", "2020-28", "2020-29", "2020-30",
> >>> "2020-31", "2020-32", "2020-33", "2020-34", "2020-35", "2020-36",
> >>> "2020-37", "2020-38", "2020-39", "2020-40", "2020-41", "2020-42",
> >>> "2020-43", "2020-44", "2020-45", "2020-46", "2020-47", "2020-48",
> >>> "2020-49", "2020-50", "2020-51", "2020-52", "2020-53", "2021-01",
> >>> "2021-02", "2021-03", "2021-04", "2021-05", "2021-06")
> >>>
> >>
> >>
> >>     [[alternative HTML version deleted]]
> >>
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> >>
> 
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
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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.