Coerces and validates a string to a standard CASRN format

This function attempts to convert a string into a valid Chemical Abstracts Service Registry Number (CASRN). It handles common data quality issues such as extra non-digit characters, missing hyphens, and leading zeros. The function extracts all digits, trims any leading zeros, formats the result into the standard "xx-yy-z" structure, and then validates it using the is_cas() check-digit algorithm.

Usage

as_cas(x)

Arguments

x

A character vector of potential CASRN strings.

Value

A character vector of the same length as x. Returns the correctly formatted, canonical CASRN string if valid, otherwise returns NA_character_.

See also

is_cas() for the underlying validation logic.

Examples

# Handles standard and padded formats
as_cas("50-00-0")
#> [1] "50-00-0"
as_cas("0050-00-0") # Padded with leading zeros
#> [1] "50-00-0"
as_cas("000575-38-2") # Another padded example
#> [1] "575-38-2"

# Handles extra characters and missing hyphens
as_cas("CAS: 7732-18-5")
#> [1] "7732-18-5"
as_cas("50000")
#> [1] "50-00-0"

# Returns NA for invalid CASRNs
as_cas("50-00-1") # Invalid check digit
#> [1] NA
as_cas("not-a-casrn")
#> [1] NA