| weekdays {base} | R Documentation |
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.
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"), ...)
x |
an object inheriting from class |
abbreviate |
logical. Should the names be abbreviated? |
origin |
an length-one object inheriting from class
|
... |
arguments for other methods. |
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.
All time calculations in R are done ignoring leap-seconds.
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. Alternatively (especially if the components
are desired as character strings), use strftime.
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. ## in the proleptic Julian calendar. To more recently, in ## 'Terrestrial Time' which differs from UTC by a few seconds ## See http://en.wikipedia.org/wiki/Terrestrial_Time julian(Sys.Date(), -2440588) # from a day floor(as.numeric(julian(Sys.time())) + 2440587.5) # from a date-time