derive_vars_aage: Derive Analysis Age

Description

Derives analysis age (AAGE) and analysis age unit (AAGEU).

Note: This is a wrapper function for the more generic derive_vars_duration().

Usage

derive_vars_aage(
  dataset,
  start_date = BRTHDT,
  end_date = RANDDT,
  age_unit = "YEARS",
  type = "interval"
)

Value

The input dataset with AAGE and AAGEU added

Arguments

dataset

Input dataset

The variables specified by the start_date and end_date arguments are expected to be in the dataset.

start_date

The start date

A date or date-time object is expected.

Refer to derive_vars_dt() to impute and derive a date from a date character vector to a date object.

Default: BRTHDT

end_date

The end date

A date or date-time object is expected.

Refer to derive_vars_dt() to impute and derive a date from a date character vector to a date object.

Default: RANDDT

age_unit

Age unit

The age is derived in the specified unit

Permitted Values (case-insensitive):

For years: "year", "years", "yr", "yrs", "y"

For months: "month", "months", "mo", "mos"

For weeks: "week", "weeks", "wk", "wks", "w"

For days: "day", "days", "d"

For hours: "hour", "hours", "hr", "hrs", "h"

For minutes: "minute", "minutes", "min", "mins"

For seconds: "second", "seconds", "sec", "secs", "s"

type

lubridate duration type.

See below for details.

Default: "duration"

Permitted Values: "duration", "interval"

Details

The duration is derived as time from start to end date in the specified output unit. If the end date is before the start date, the duration is negative. The start and end date variable must be present in the specified input dataset.

The lubridate package calculates two types of spans between two dates: duration and interval. While these calculations are largely the same, when the unit of the time period is month or year the result can be slightly different.

The difference arises from the ambiguity in the length of "1 month" or "1 year". Months may have 31, 30, 28, or 29 days, and years are 365 days and 366 during leap years. Durations and intervals help solve the ambiguity in these measures.

The interval between 2000-02-01 and 2000-03-01 is 1 (i.e. one month). The duration between these two dates is 0.95, which accounts for the fact that the year 2000 is a leap year, February has 29 days, and the average month length is 30.4375, i.e. 29 / 30.4375 = 0.95.

For additional details, review the lubridate time span reference page.

Examples

Run this code

library(tibble)
library(lubridate)

data <- tribble(
  ~BRTHDT, ~RANDDT,
  ymd("1984-09-06"), ymd("2020-02-24")
)

derive_vars_aage(data)