Calculate the actual age in completed years between two dates

Computes the exact age in full years at the time of an event (e.g., diagnosis, death, or survey) by comparing a person's birth date to the date of the event.

calc_age(birth_date, onset_date)

Arguments

birth_date: A vector of birth dates in Date format.
onset_date: A vector of corresponding event dates in Date format (e.g., date of diagnosis).

Value

A numeric vector of ages in years, with the same length as birth_date and onset_date.

Details

This function calculates age in completed years, taking into account whether the birthday has occurred before the event date in the given year. If birth_date or onset_date contains NA, the corresponding result will be NA.

Examples

# Generate random birth dates
set.seed(123)
sdate <- as.Date("1960-01-01")
edate <- as.Date("1980-12-31")
bdate <- sample(seq(sdate, edate, by = "1 day"), 100, replace = TRUE)

# Generate random event dates
sdate <- as.Date("2020-01-01")
edate <- as.Date("2023-07-08")
event <- sample(seq(sdate, edate, by = "1 day"), 100, replace = TRUE)

# Calculate ages
ages <- calc_age(bdate, event)
head(ages)
#> [1] 54 55 54 60 48 54
# Handle missing values
bdate[1] <- NA
event[2] <- NA
calc_age(bdate, event)[1:5]
#> [1] NA NA 54 60 48