as.period: Change an object to a period.

Description

as.period changes Interval, Duration, difftime and numeric class objects to Period class objects with the specified units.

Usage

as.period(x, unit, ...)

Arguments

an interval, difftime, or numeric object

unit

A character string that specifies which time units to build period in. unit is only implemented for the as.period.numeric method.

...

additional arguments to pass to as.period

Value

a period object

Details

Users must specify which time units to measure the period in. The exact length of each time unit in a period will depend on when it occurs. See Period-class and new_period. The choice of units is not trivial; units that are normally equal may differ in length depending on when the time period occurs. For example, when a leap second occurs one minute is longer than 60 seconds.

Because periods do not have a fixed length, they can not be accurately converted to and from Duration objects. Duration objects measure time spans in exact numbers of seconds, see Duration-class. Hence, a one to one mapping does not exist between durations and periods. When used with a Duration object, as.period provides an inexact estimate; the duration is broken into time units based on the most common lengths of time units, in seconds. Because the length of months are particularly variable, a period with a months unit can not be coerced from a duration object. For an exact transformation, first transform the duration to an interval with as.interval.

Examples

Run this code

span <- new_interval(as.POSIXct("2009-01-01"), as.POSIXct("2010-02-02 01:01:01")) #interval
# 2009-01-01 CST--2010-02-02 01:01:01 CST
as.period(span)
# 1 year, 1 month, 1 day, 1 hour, 1 minute and 1 second