day.of.week: Convert between Julian and Calendar Dates
Usage
julian(m, d, y, origin = c(month = 1, day = 1, year = 1970))
month.day.year(jul, origin = c(month = 1, day = 1, year = 1970))
leap.year(y)
day.of.week(month, day, year)
Arguments
m
vector of month numbers.
d
vector of day numbers.
y
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 options(chron.origin) if this is non-null,
otherwise c(month = 1, day = 1, year = 1970).
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.