weekdays                package:base                R Documentation

Extract Parts of a POSIXt or Date Object

Description:

     Extract the weekday, month or quarter, or the Julian time (days
     since some origin).  These are generic functions: the methods for
     the internal date-time classes are documented here.

Usage:

     weekdays(x, abbreviate)
     ## S3 method for class 'POSIXt':
     weekdays(x, abbreviate = FALSE)
     ## S3 method for class 'Date':
     weekdays(x, abbreviate = FALSE)

     months(x, abbreviate)
     ## S3 method for class 'POSIXt':
     months(x, abbreviate = FALSE)
     ## S3 method for class 'Date':
     months(x, abbreviate = FALSE)

     quarters(x, abbreviate)
     ## S3 method for class 'POSIXt':
     quarters(x, ...)
     ## S3 method for class 'Date':
     quarters(x, ...)

     julian(x, ...)
     ## S3 method for class 'POSIXt':
     julian(x, origin = as.POSIXct("1970-01-01", tz="GMT"), ...)
     ## S3 method for class 'Date':
     julian(x, origin = as.Date("1970-01-01"), ...)

Arguments:

       x: an object inheriting from class '"POSIXt"' or '"Date"'.

abbreviate: logical.  Should the names be abbreviated?

  origin: an length-one object inheriting from class '"POSIXt"' or
          '"Date"'.

     ...: arguments for other methods.

Value:

     'weekdays' and 'months' return a character vector of names in the
     locale in use.

     'quarters' returns a character vector of '"Q1"' to '"Q4"'.

     'julian' returns the number of days (possibly fractional) since
     the origin, with the origin as a '"origin"' attribute.

Note:

     Other components such as the day of the month or the year are very
     easy to compute: just use 'as.POSIXlt' and extract the relevant
     component.

See Also:

     'DateTimeClasses', 'Date'

Examples:

     weekdays(.leap.seconds)
     months(.leap.seconds)
     quarters(.leap.seconds)

     ## Julian Day Number (JDN, http://en.wikipedia.org/wiki/Julian_day)
     ## is the number of days since noon UTC on the first day of 4317 BC.
     julian(Sys.Date(), -2440588) # for a day
     floor(as.numeric(julian(Sys.time())) + 2440587.5) # for a date-time

