day.of.week: Convert between Julian and Calendar Dates
Description
Utility functions to convert between Julian dates (numbers of days
since an origin, by default 1970-01-01) and calendar dates given by
year, month, and day within the month.
Usage
## S3 method for class 'default':
julian(x, d, y, origin., \dots)
month.day.year(jul, origin.)
leap.year(y)
day.of.week(month, day, year)
Arguments
x, month
vector of month numbers.
d, day
vector of day numbers.
y, year
vector of years.
jul
vector of Julian Dates, i.e., number of days since
origin..
origin.
vector specifying the origin as month, day, and year.
If missing, it defaults to getOption("chron.origin") if this
is non-null, otherwise
c(month = 1, day = 1, year = 1970).
...
further arguments to be passed to or from methods.
Value
A vector of Julian dates (number of days since origin.) when
julian() is called, or a list with members month,
day, year corresponding to the input Julian dates if
month.day.year() is called. leap.year() returns a
logical vector indicating whether the corresponding year is a leap
year.
day.of.week() returns a number between 0 and 6 to specify day
of the week--0 refers to Sunday.
These functions were taken from Becker, Chambers, and Wilks (1988),
and were slightly modified to take chron and dates
objects; some also take the extra argument origin..