使用 lubridate 从周数中查找月份

Question

I have this list of dates:

library(lubridate)
my.dates = ymd(c("2013-12-14", "2014-01-18", "2014-01-27", "2013-12-13", "2013-12-29", "2013-12-06"))

The following lubridate::week functions outputs a numeric vector when I convert these dates to week numbers:

week(my.dates)
[1] 50  3  4 50 52 49

Can I get lubridate to output a date ("POSIXct" "POSIXt") object that converts my.dates to a week number and year number. So output should be a date object (not a character or numeric vector) formatted something like this:

[1] "50-2013" "3-2014"   "4-2014"   "50-2013" "52-2013" "49-2013"

I'm specifically interested in a solution that uses lubridate .

Answer 1

To convert my.dates to a week-year character vector try the following where week and year are lubridate functions:

> paste(week(my.dates), year(my.dates), sep = "-")
[1] "50-2013" "3-2014"  "4-2014"  "50-2013" "52-2013" "49-2013"

The sample output in the question did not use leading zeros for the week but if leading zeros were desired for the week then:

> sprintf("%02d-%d", week(my.dates), year(my.dates))
[1] "50-2013" "03-2014" "04-2014" "50-2013" "52-2013" "49-2013"

The above are character representations of week-year and do not uniquely identify a date nor can such a format represent a POSIXt object.