The chapter headings can be converted into the full set of their children,
and then used to look-up which chapter, sub-chapter, or 'major' a given code
belongs. Always returns a map with short-form ICD-9 codes. These can be
converted in bulk with lapply
and short_to_decimal
.
chapters_to_map(x, defined = TRUE)
Either a chapter list itself, or the name of one, e.g.
icd9_sub_chapters
Single logical value, if TRUE
, the default, only
officially defined ICD-9 (currently ICD-9-CM) codes will be used in the
expansion, not any syntactically possible ICD-9 code.