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.
Value
a vector of Julian dates.
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.
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.
Terry Therneau and Thomas Lumley and Kjetil Halvorsen
and Kurt Hornik (2012). date: Functions for handling
dates. R package version 1.2-33.
See Also
see documentation and other functions in the package date