Calculates age in years based on a reference date, which is the system date at default.

## Usage

age(x, reference = Sys.Date(), exact = FALSE, na.rm = FALSE, ...)

## Arguments

x

date(s), character (vectors) will be coerced with as.POSIXlt()

reference

reference date(s) (default is today), character (vectors) will be coerced with as.POSIXlt()

exact

a logical to indicate whether age calculation should be exact, i.e. with decimals. It divides the number of days of year-to-date (YTD) of x by the number of days in the year of reference (either 365 or 366).

na.rm

a logical to indicate whether missing values should be removed

...

arguments passed on to as.POSIXlt(), such as origin

## Value

An integer (no decimals) if exact = FALSE, a double (with decimals) otherwise

## Details

Ages below 0 will be returned as NA with a warning. Ages above 120 will only give a warning.

This function vectorises over both x and reference, meaning that either can have a length of 1 while the other argument has a larger length.

To split ages into groups, use the age_groups() function.

## Examples

# 10 random pre-Y2K birth dates
df <- data.frame(birth_date = as.Date("2000-01-01") - runif(10) * 25000)

df$age <- age(df$birth_date)

df$age_exact <- age(df$birth_date, exact = TRUE)

# add age at millenium switch
df$age_at_y2k <- age(df$birth_date, "2000-01-01")

df
#>    birth_date age age_exact age_at_y2k
#> 1  1960-01-29  63  63.12603         39
#> 2  1987-04-14  35  35.92055         12
#> 3  1976-01-12  47  47.17260         23
#> 4  1951-10-24  71  71.39178         48
#> 5  1982-07-07  40  40.69041         17
#> 6  1997-02-24  26  26.05479          2
#> 7  1940-02-14  83  83.08219         59
#> 8  1975-04-24  47  47.89315         24
#> 9  1996-09-25  26  26.47123          3
#> 10 1949-01-29  74  74.12603         50