stRoke/R/age_calc.R
2023-01-12 14:32:27 +01:00

127 lines
4.1 KiB
R

#' Calculate age in years, months, or days
#'
#' @param dob Date of birth
#' @param enddate End date for age calculation (default is Sys.Date())
#' @param units Units for age calculation (default is "years").
#' Can be c("days", "months", "years")
#' @param precise Option to calculate age precisely (default is TRUE)
#' @return numeric vector length 1
#' @export
#'
#' @examples
#' trunc(age_calc(as.Date("1945-10-23"),as.Date("2018-09-30")))
#' @references
#' A similar functionality is achievable
#' with \code{\link[lubridate]{time_length}}
#'
#' Becker, J.P. (2020). eeptools: An R Package for Teaching and Learning
#' Ecology and Evolutionary Biology. Journal of Statistical Software,
#' 93(2), 1-27.
#' @source \doi{10.18637/jss.v093.i02}
#'
#' @keywords date time age
age_calc<-function (dob, enddate = Sys.Date(), units = "years", precise = TRUE)
{
if (!inherits(dob, "Date") | !inherits(enddate, "Date")) {
stop("Both dob and enddate must be Date class objects")
}
if (length(dob)==1 && enddate < dob) {
stop("End date must be a date after date of birth")
}
if (length(dob)>1 && any(enddate < dob)) {
stop("End date must be a date after date of birth")
}
start <- as.POSIXlt(dob)
end <- as.POSIXlt(enddate)
if (precise) {
start_is_leap <- ifelse(start$year%%400 == 0, TRUE,
ifelse(start$year%%100 == 0,
FALSE,
ifelse(start$year%%4 == 0, TRUE, FALSE)))
end_is_leap <- ifelse(end$year%%400 == 0, TRUE,
ifelse(end$year%%100 == 0,
FALSE,
ifelse(end$year%%4 == 0, TRUE, FALSE)))
}
if (units == "days") {
result <- as.numeric(difftime(end, start, units = "days"))
}
else if (units == "months") {
months <- vapply(
mapply(
seq,
as.POSIXct(start),
as.POSIXct(end),
by = "months",
SIMPLIFY = FALSE
),
length,
numeric(1)
) - 1
if (precise) {
month_length_end <- ifelse(end$mon == 1 & end_is_leap,
29, ifelse(end$mon == 1, 28,
ifelse(end$mon %in% c(3, 5, 8, 10),
30, 31)))
month_length_prior <- ifelse((end$mon - 1) == 1 &
start_is_leap, 29,
ifelse((end$mon - 1) == 1, 28,
ifelse((end$mon - 1) %in%
c(3, 5, 8, 10), 30, 31)))
month_frac <- ifelse(end$mday > start$mday,
(end$mday - start$mday)/month_length_end,
ifelse(end$mday < start$mday,
(month_length_prior -
start$mday)/month_length_prior +
end$mday/month_length_end, 0))
result <- months + month_frac
}
else {
result <- months
}
}
else if (units == "years") {
years <- vapply(
mapply(
seq,
as.POSIXct(start),
as.POSIXct(end),
by = "years",
SIMPLIFY = FALSE
),
length,
numeric(1)
) - 1
if (precise) {
start_length <- ifelse(start_is_leap, 366, 365)
end_length <- ifelse(end_is_leap, 366, 365)
start_day <- ifelse(start_is_leap & start$yday >=
60, start$yday - 1, start$yday)
end_day <- ifelse(end_is_leap & end$yday >= 60, end$yday -
1, end$yday)
year_frac <- ifelse(start_day <
end_day, (end_day - start_day)/end_length,
ifelse(start_day > end_day,
(start_length - start_day)/start_length +
end_day/end_length, 0))
result <- years + year_frac
}
else {
result <- years
}
}
else {
stop("Unrecognized units. Please choose years, months, or days.")
}
result
}