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rdplyrpurrrlubridate

R lubridate customise week_start by year

Here is my example data, and I want to customise week_start by year in wday function from lubridate package

mydate <- data.frame(Date = c("13/09/2021", "13/09/2020", "13/09/2019", "13/09/2018"))

For instance, the start of the week will be year %% 7. But I got the following error when I run my code

numerical expression has 4 elements: only the first used 

library(lubridate)
library(dplyr)

mydate2 <- mydate %>%
  mutate(Date = ymd(as.Date(as.factor(Date), format = "%d/%m/%Y")),
         years = year(Date),
         days = wday(Date, label = TRUE, week_start = years %% 7))

I think I need to use the map function from purrr. I have tried few times, but it didn't work.

Thanks a lot.

Solution

  • You may use map2_chr to have a custom week_start for every Date based on year value.

    library(dplyr)
library(lubridate)

mydate %>%
  mutate(Date = as.Date(Date, format = "%d/%m/%Y"),
         years = year(Date),
         days = map2_chr(Date, years, 
                  ~as.character(wday(.x, label = TRUE, week_start = .y %% 7))))


#        Date years days
#1 2021-09-13  2021  Mon
#2 2020-09-13  2020  Sun
#3 2019-09-13  2019  Fri
#4 2018-09-13  2018  Thu