Unlike get_icd9cm2014_leaf and friends, these data frames
contain the full structure of the ICD-9-CM scheme up to the three-digit
codes. Unlike the equivalent ICD-10-CM data frames (e.g.,
icd10cm2019), they do not have columns indicating billable/leaf
status, or chapter designations.
icd9cm_hierarchy is the deprecated name, which currently points to the
final ICD-9-CM 2014 release. 2011 -- 2014 are in fact identical. These are
generated dynamically by parsing an awkward RTF file, and only the 2011 --
2014 data has been tested and used thoroughly.
Format: data frame