Schedule the nth events of a period

Given a schedule of events, create a new schedule of only the nth occurrences within a given period.

on_nth(n, x, within_given)

on_first(x, within_given)

on_second(x, within_given)

on_third(x, within_given)

on_fourth(x, within_given)

on_last(x, within_given)

Arguments

n	A single integer specifying which event to select. A negative integer will select the nth last event (i.e. -1L will select the last event of the period, -2L will return the second last etc).
x	A schedule from which to select events.
within_given	A period from within which to select events. Can be either: A string shortcut for a period type: either "day", "week", "month", "quarter" or "year". Or, A date accessor function. Eg. lubridate::month().

Value

A schedule object.

Details

Convenience functions are provided for the first, second, third, fourth and last events of a given period.

All functions accept arbitrarily complex schedules. For example, if you wanted a schedule of events occurring on the 12th either Tuesday or Thursday of the quarter you would use: on_nth(12, on_wday("Tue", "Thu"), within_given = "quarter").

Examples

tuesday <- on_wday("Tue")

second_tuesday_month <- on_second(tuesday, within_given = "month")
schedule_days(second_tuesday_month, during = 2000)
#>  [1] "2000-01-11" "2000-02-08" "2000-03-14" "2000-04-11" "2000-05-09"
#>  [6] "2000-06-13" "2000-07-11" "2000-08-08" "2000-09-12" "2000-10-10"
#> [11] "2000-11-14" "2000-12-12"

last_tuesday_year <- on_last(tuesday, within_given = "year")
schedule_days(last_tuesday_year, during = 2000)
#> [1] "2000-12-26"

tenth_tuesday_quarter <- on_nth(10, tuesday, within_given = "quarter")
schedule_days(tenth_tuesday_quarter, during = 2000)
#> [1] "2000-03-07" "2000-06-06" "2000-09-05" "2000-12-05"

tues_or_thurs <- on_wday("Tue", "Thu")

tenth_tues_or_thurs_quarter <- on_nth(10, tues_or_thurs, within_given = "quarter")
schedule_days(tenth_tues_or_thurs_quarter, during = 2000)
#> [1] "2000-02-03" "2000-05-04" "2000-08-03" "2000-11-02"