weekdays {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

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