cal.yr {Epi} | R Documentation |
Dates are converted to a numerical value, giving the calendar year as
a fractional number. 1 January 1970 is converted to 1970.0, and other
dates are converted by assuming that years are all 365.25 days long,
so inaccuracies may arise, for example, 1 Jan 2000 is converted to
1999.999. Differences between converted values will be 1/365.25 of the
difference between corresponding Date
objects.
cal.yr(x, format)
x |
A factor or character vector, representing a date in format
format , or an object of class
Date ,
POSIXlt ,
POSIXct ,
date ,
dates or
chron (the latter two requires the chron package). |
format |
Format of the date values if x is factor or character |
cal.yr
returns a numerical vector of the same length as
x
.
Bendix Carstensen, Steno Diabetes Center & Dept. of Biostatistics, University of Copenhagen, bxc@steno.dk, http://www.pubhealth.ku.dk/~bxc
birth <- c("14/07/1952","01/04/1954","10/06/1987","16/05/1990", "01/01/1996","01/01/1997","01/01/1998","01/01/1999") ( bt.yr <- cal.yr( birth, format="%d/%m/%Y" ) ) # To get readable output: data.frame( birth, bt.yr )