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Extract Date of Birth (DoB) from the CHI number

Source: R/dob_from_chi.R
dob_from_chi.Rd

dob_from_chi takes a CHI number or a vector of CHI numbers and returns the Date of Birth (DoB) as implied by the CHI number(s). If the DoB is ambiguous it will return NA.

Usage

dob_from_chi(
  chi_number,
  min_date = NULL,
  max_date = NULL,
  chi_check = TRUE,
  check_mod11 = TRUE,
  check_mod10 = TRUE
)

Arguments

chi_number

a CHI number or a vector of CHI numbers with character class.

min_date, max_date

optional min and/or max dates that the DoB could take as the century needs to be guessed. Must be either length 1 for a 'fixed' date or the same length as chi_number for a date per CHI number. min_date can be date based on common sense in the dataset, whilst max_date can be date when an event happens such as discharge date.

chi_check

logical, optionally skip checking the CHI for validity which will be faster but should only be used if you have previously checked the CHI(s). The default (TRUE) will check the CHI numbers.

check_mod11, check_mod10

Logical values (TRUE or FALSE, default is TRUE). By default, a CHI that passes either the modulo 10 or the modulo 11 check will be considered valid. Historically, CHIs only used modulo 11 for their check digit; however, starting in August 2026, some CHIs will only pass if they meet the modulo 10 criteria. Implementation of Mod 10 CHI numbers is scheduled for August 2026. From this date, CHI numbers are valid if they pass either a Mod 11 check or a Mod 10 check.

Value

a date vector of DoB. It will be the same length as chi_number.

Examples

dob_from_chi("0101336489")
#> [1] "1933-01-01"

library(tibble)
library(dplyr)
data <- tibble(chi = c(
  "0101336489",
  "0101405073",
  "0101625707"
), adm_date = as.Date(c(
  "1950-01-01",
  "2000-01-01",
  "2020-01-01"
)))

data %>%
  mutate(chi_dob = dob_from_chi(chi))
#> # A tibble: 3 × 3
#>   chi        adm_date   chi_dob   
#>   <chr>      <date>     <date>    
#> 1 0101336489 1950-01-01 1933-01-01
#> 2 0101405073 2000-01-01 1940-01-01
#> 3 0101625707 2020-01-01 1962-01-01

data %>%
  mutate(chi_dob = dob_from_chi(chi,
    min_date = as.Date("1930-01-01"),
    max_date = adm_date
  ))
#> # A tibble: 3 × 3
#>   chi        adm_date   chi_dob   
#>   <chr>      <date>     <date>    
#> 1 0101336489 1950-01-01 1933-01-01
#> 2 0101405073 2000-01-01 1940-01-01
#> 3 0101625707 2020-01-01 1962-01-01