mdy.date              package:survival              R Documentation

Convert to Julian Dates

Description:

     Given a month, day, and year, returns the number of days since
     January 1, 1960.

Usage:

     mdy.date(month, day, year, nineteen = TRUE, fillday = FALSE,
              fillmonth = FALSE)

Arguments:

   month: vector of months.

     day: vector of days.

    year: vector of years.

nineteen: if 'TRUE', year values between 0 and 99 are assumed to be in
          the 20th century A.D.; otherwise, if 'FALSE', they are
          assumed to be in the 1st century A.D.

 fillday: if 'TRUE', then missing days are replaced with 15.

fillmonth: if 'TRUE', then a missing month causes the month and day to
          be set to 7/1.

Details:

     The date functions are particularly useful in computing time
     spans, such as number of days on test, and similar functions can
     be found in other statistical packages.  The baseline date of Jan
     1, 1960 is, of course, completely arbitrary (it is the same one
     used by SAS).

     The 'fillday' and 'fillmonth' options are perhaps useful only to
     the author and a very few others: we sometimes deal with patients
     whose birth date was in the 1800's, and only the month or even
     only the year is known.  When the interval is greater than 80
     years, a filler seems defensible.

Value:

     a vector of Julian dates.

References:

     Press, W. H., Teukolsky, S. A., Vetterling, W. T., and Flannery,
     B. P. (1992). _Numerical Recipes: The Art of Scientific Computing
     (Second Edition)_. Cambridge University Press.

See Also:

     'date.mmddyy',  'date.ddmmmyy', 'date.mmddyyyy'

Examples:

     mdy.date(3, 10, 53)
     xzt <-1:10
     xzy <- as.date(xzt)
     test <- data.frame(x = xzt, date = xzy)
     summary(test)

