Create a period object.

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Description

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.

Usage

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period(num = NULL, units = "second", ...)

is.period(x)

Arguments

num

a numeric vector that lists the number of time units to be included in the period. From v1.6.0 num can also be a character vector that specifies durations in a convenient shorthand format. All unambiguous name units and abbreviations are supported. One letter "m" stands for months, "M" stands for minutes. See examples.

units

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. When num is character, this argument is ignored.

...

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 num or ... are present. If both are present, the periods are concatenated.

x

an R object

Details

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 years, months, weeks, days, hours, minutes, and 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 %m+% and add_with_rollback for alternative operations.

Value

a period object

See Also

Period-class, quick_periods, %m+%, add_with_rollback

Examples

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period(c(90, 5), c("second", "minute"))
#  "5M 90S"
period(-1, "days")
period(c(3, 1, 2, 13, 1), c("second", "minute", "hour", "day", "week"))
period(c(1, -60), c("hour", "minute"))
period(0, "second")
period (second = 90, minute = 5)
period(day = -1)
period(second = 3, minute = 1, hour = 2, day = 13, week = 1)
period(hour = 1, minute = -60)
period(second = 0)
period(c(1, -60), c("hour", "minute"), hour = c(1, 2), minute = c(3, 4))
period("2M 1sec")
period("2hours 2minutes 1second")
period("2d 2H 2M 2S")
period("2days 2hours 2mins 2secs")
# Missing numerals default to 1. Repeated units are added up.
duration("day day")
# Comparison with characters is supported from v1.6.0.
duration("day 2 sec") > "day 1sec"
is.period(as.Date("2009-08-03")) # FALSE
is.period(period(months= 1, days = 15)) # TRUE

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