A 'rollforward' function?

[kputschko]

I'm looking for a quicker way to roll a date to the end of the given month. Currently it takes two functions, ceiling_date and subtracting days.

library(lubridate)

date_1 <- ymd("2020-01-15")

# rollback is simple and great
rollback(date_1)
rollback(date_1, roll_to_first = TRUE)

# but rolling forward looks a little clunky
ceiling_date(date_1, unit = "month") - days(1)
>"2020-01-31"

# maybe add an option to rollback?
rollback(date_1, roll_to_last = TRUE)
>"2020-01-31"

# or create a new function?
rollforward(date_1)
>"2020-01-31"

[vspinu]

"faster" as in "type faster" or "faster execution speed"?

I think it makes sense to add it for completeness, as a counterpart of rollback.

[seasmith]

rollforward <- function (dates, roll_to_first = FALSE, preserve_hms = TRUE) 
{
  if (length(dates) == 0) 
    return(dates)
  day(dates) <- 1
  if (!preserve_hms) {
    hour(dates) <- 0
    minute(dates) <- 0
    second(dates) <- 0
  }
  if (roll_to_first) {
    dates + months(1)
  }
  else {
    dates + months(1) - days(1)
  }
}

[UweBlock]

Just saw the new function being mentioned in News.md.

For the sake of consistency with rollback(), I had expected

library(lubridate)

date_1 <- ymd("2020-01-15")

rollback(date_1)
# "2019-12-31" = last day of preceeding month

rollforward(date_1)
# "2020-02-01" = first day of succeeding month
#  equivalent to
ceiling_date(date_1, unit = "month")

rollback(date_1, roll_to_first = TRUE)
# "2020-01-01" = first day of given month

rollforward(date_1, roll_to_last = TRUE)
# "2020-01-31" = last day of given month

[vspinu]

This is an alternative notion of a symmetry, or probably better asymetry. What you propose is the mirror of rollback.

The advantage of the current design is that there is no extra argument (roll_to_last) and reasoning about the code is simpler because there is one pattern to remember - by default roll to last day, with the argument to first day etc.