Derive Age in Years

Source: R/derive_vars_aage.R

Converts the given age variable (age_var) to the unit 'years' from the current units given in the age_var+U variable or age_unit argument and stores in a new variable (new_var).

derive_var_age_years(dataset, age_var, age_unit = NULL, new_var)

Arguments

dataset

Input dataset

The variables specified by the age_var argument are expected to be in the dataset.

Default value

none

age_var

Age variable.

A numeric object is expected.

Default value

none

age_unit

Age unit.

The age_unit argument is only expected when there is NOT a variable age_var+U in dataset. This gives the unit of the age_var variable and is used to convert AGE to 'years' so that grouping can occur.

Permitted values

'years', 'months', 'weeks', 'days', 'hours', 'minutes', 'seconds'

Default value

NULL

new_var

New age variable to be created in years. The returned values are doubles and NOT integers. '

Default value

none

Value

The input dataset (dataset) with new_var variable added in years.

Details

This function is used to convert an age variable into the unit 'years' which can then be used to create age groups. The resulting column contains the equivalent years as a double. Note, underlying computations assume an equal number of days in each year (365.25).

See also

derive_vars_duration()

ADSL Functions that returns variable appended to dataset: derive_vars_aage(), derive_vars_extreme_event(), derive_vars_period()

Examples

library(tibble)

# Derive age with age units specified
data <- tribble(
  ~AGE, ~AGEU,
  27, "days",
  24, "months",
  3, "years",
  4, "weeks",
  1, "years"
)

derive_var_age_years(data, AGE, new_var = AAGE)
#> # A tibble: 5 × 3
#>     AGE AGEU     AAGE
#>   <dbl> <chr>   <dbl>
#> 1    27 days   0.0739
#> 2    24 months 2     
#> 3     3 years  3     
#> 4     4 weeks  0.0767
#> 5     1 years  1     

# Derive age without age units variable specified
data <- tribble(
  ~AGE,
  12,
  24,
  36,
  48
)
derive_var_age_years(data, AGE, age_unit = "months", new_var = AAGE)
#> # A tibble: 4 × 2
#>     AGE  AAGE
#>   <dbl> <dbl>
#> 1    12     1
#> 2    24     2
#> 3    36     3
#> 4    48     4