R：从日期获取正确的周数（年初/年末）

Question

I struggle with getting my code correct. From my dataset I want to assign 'year+week' to all the dates but have not succeeded. The output I get is displayed below:

referenceTime	Week
31-12-2020	2020 - W53
...	...
01-01-2017	2017 - W52

01-01-2017 is in week 52 in 2016, and not 2017. It looks like a lot of other users also have difficulties with R not registrering beginning and ending of years, so the weeks get wrong. I have looked at other responses on StackOverflow but have not succeeded to find something that works for my code. The code I have now is this:

data$Week <- format(df2$referenceTime, format="%YW%V")

I am open for other suggestions, I see that some also use the lubridate package.

Hope someone can help me with this issue.

Answer 1

You can use %G The week-based year instead of %Y :

format(x, format="%G-%V")
#[1] "2020-53" "2016-52"

Or use %U instead of %V :

format(x, format="%Y-%U")
#[1] "2020-52" "2017-01"

Data:

x <- as.Date(c("2020-12-31", "2017-01-01"))