parseQuanDeyoSas: parse original SAS code defining Quan's update of Deyo...
In icd9: Tools for Working with ICD-9 Codes, and Finding Comorbidities

As with parseAhrqSas, this function reads SAS code, and in, a very limited way, extracts definitions. In this case the code uses LET statements, with strings or lists of strings. This saves and invisibly returns a list with names corresponding to the comorbidities and values as a vector of 'short' form (i.e. non-decimal) ICD9 codes. Unlike parseAhrqSas, there are no ranges defined, so this interpretation is simpler.

With thanks to Dr. Quan, I have permission to distribute his SAS code. Previously, the SAS code would be downloaded from the University of Manitoba at http://mchp-appserv.cpe.umanitoba.ca/concept/ICD9_E_Charlson.sas.txt. There are structural differences between this version and the version directly from Dr. Quan, however, the parsing results in identical data.

1 2	parseQuanDeyoSas(sasPath = NULL, condense = FALSE, save = FALSE, path = "data")

`sasPath`	single character string containing path or URL for some SAS code. The source SAS code is stored in extdata or at the location specified in URL. In development mode in `devtools`, this is actually inst/extdata. This function is internal, since it is used to generate data which ends up in the distributed package. However, the package user can verify that the code creates the distributed R data. Also, changes to the original SAS code can be used to regenerate the R data by the user, without waiting for a package release.
`condense`	logical whether to condense the result ranges to the minimal set of parent ICD-9 codes which exactly define the list. Defaults to `FALSE` so that the saved list will allow rapid look-up of codes without further processing. Small memory versus time trade-off.
`save`	logical whether to save the result in the source tree. Defaults to `FALSE`.
`path`	path to directory to save the data. This is typically the data folder in the devleopment source tree. Defaults to `"~/icd9/data"`. Could possibly avoid hard-coding path with devtools functions.