Create a period object.
period creates a period object with the specified values. period
provides the behaviour of
period in a way that is more
suitable for automating within a function.
period(num = NULL, units = "second", ...)is.period(x)
- a numeric vector that lists the number of time units to be included in the period
- a character vector that lists the type of units to be used. The units in units are matched to the values in num according to their order.
- a list of time units to be included in the period and their
amounts. Seconds, minutes, hours, days, weeks, months, and years are
supported. Normally only one of
...are present. If both are present, the periods are concatenated.
- an R object
Within a Period object, time units do not have a fixed length (except for seconds) until they are added to a date-time. The length of each time unit will depend on the date-time to which it is added. For example, a year that begins on 2009-01-01 will be 365 days long. A year that begins on 2012-01-01 will be 366 days long. When math is performed with a period object, each unit is applied separately. How the length of a period is distributed among its units is non-trivial. For example, when leap seconds occur 1 minute is longer than 60 seconds.
Periods track the change in the "clock time" between two date-times. They are measured in common time related units: years, months, days, hours, minutes, and seconds. Each unit except for seconds must be expressed in integer values.
Period objects can be easily created with the helper functions
seconds. These objects can be added to and subtracted
to date-times to create a user interface similar to object oriented programming.
Note: Arithmetic with periods can results in undefined behavior when
non-existent dates are involved (such as February 29th). Please see
Period-class for more details and
add_with_rollback for alternative operations.
a period object
period(c(90, 5), c("second", "minute")) # "5M 90S" period(-1, "days") # "-1d 0H 0M 0S" period(c(3, 1, 2, 13, 1), c("second", "minute", "hour", "day", "week")) # "20d 2H 1M 3S" period(c(1, -60), c("hour", "minute")) # "1H -60M 0S" period(0, "second") # "0S" period (second = 90, minute = 5) # "5M 90S" period(day = -1) # "-1d 0H 0M 0S" period(second = 3, minute = 1, hour = 2, day = 13, week = 1) # "20d 2H 1M 3S" period(hour = 1, minute = -60) # "1H -60M 0S" period(second = 0) # "0S" period(c(1, -60), c("hour", "minute"), hour = c(1, 2), minute = c(3, 4)) # "1H -60M 0S" "1H 3M 0S" "2H 4M 0S" is.period(as.Date("2009-08-03")) # FALSE is.period(period(months= 1, days = 15)) # TRUE