Calendar year {Epi} | R Documentation |
Dates are converted to a numerical value, so that 1 January
1970 is converted to 1970.0. The result is given a class
attribute, cal.yr
. The function is intended for epidemiological
use, and the dates are converted to a calendar time scale that has 4
years of equal length between 1.1.1970 and 1.1.1974 etc. The printing of
cal.yr
objects in human readable form may therefore be as much
as 3 days wrong.
cal.yr(x, format) dmy.cal.yr( d, m, y ) mdy.cal.yr( m, d, y ) ymd.cal.yr( y, m, d ) weekdays.cal.yr( x, abbreviate=FALSE ) weeks( x ) weeks.cal.yr( x ) months.cal.yr( x, abbreviate=FALSE ) print.cal.yr( x, format="%d/%m/%Y", ... )
x |
A character vector, representing a date in format
format , or an object of class POSIXt or
Date . |
d, m, y |
Numerical vectors representing, date month and year. |
format |
Optional character values giving the format for the date
if given as character. See the help page for strptime for
admissible values. |
abbreviate |
Should names be abbreviated? |
... |
Ignored, but present for compatibility with print methods |
cal.yr
returns a numerical vector of the same length as
x
. The associated print method, print.cal.yr
prints the
dates in human readable format. To see the dates as fractions of
years, use as.numeric(cy)
.
dmy.cal.yr
, mdy.cal.yr
and ymd.cal.yr
are
convenience functions for converting separate numerical variables
with date d
, month m
and year y
into dates of
class cal.yr
. These functions also accept a single character
variable as input, with two digits for day and month and four for year
and any delimiters.
weekdays.cal.yr
, weeks.cal.yr
and months.cal.yr
,
extract weekday, week number and month from calendar year
objects. weekdays
and months
return factors with 7 and
12 levels respectively, regardless of the actually occurring number of
levels. weeks
return numeric values in the range 1–52.
Bendix Carstensen, Steno Diabetes Center & Dept. of Biostatistics, University of Copenhagen, http://www.biostat.ku.dk/~bxc
birth <- c("14/07/1952", "01/04/1954", "10/06/1987") ( bt.yr <- cal.yr( birth, format="%d/%m/%Y" ) ) as.numeric( bt.yr ) weeks( bt.yr ) months( bt.yr ) ( bt.y <- dmy.cal.yr( birth ) )