icd9ChaptersToMap: convert the chapter headings to lists of codes
Description
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 en masse with lapply and icd9ShortToDecimal.
Usage
icd9ChaptersToMap(x)
Arguments
x
Either a chapter list itself, or the name of one, e.g.
icd9ChaptersSub