icd9GetValid: invalid subset of decimal or short ICD-9 codes
In jackwasey/icd9: Tools for Working with ICD-9 Codes, and Finding Comorbidities

Given vector of short or decimal ICD-9 codes, return (in the same format) those codes which are valid or invalid. Useful for generating error messages with the faulty codes if validation fails.

icd9GetValid(icd9, isShort = icd9GuessIsShort(icd9))

icd9GetValidDecimal(icd9Decimal)

icd9GetValidShort(icd9Short)

icd9GetInvalid(icd9, isShort = icd9GuessIsShort(icd9))

icd9GetInvalidDecimal(icd9Decimal)

icd9GetInvalidShort(icd9Short)

`icd9`	is a character vector or factor of ICD-9 codes. If fewer than five characters is given in a code, then the digits are greedily assigned to hundreds, then tens, then units, before the decimal parts. E.g. "10" becomes "010", not "0010".
`isShort`	single logical value which determines whether the ICD-9 code provided is in short (TRUE) or decimal (FALSE) form. Where reasonable, this is guessed from the input data.
`icd9Decimal`	character vector of ICD-9 codes. If fewer than five characters is given in a code, then the digits are greedily assigned to hundreds, then tens, then units, before the decimal parts. E.g. "10" becomes "010", not "0010"
`icd9Short`	is a character vector of ICD-9 codes. If fewer than five characters is given in a code, then the digits are greedily assigned to hundreds, then tens, then units, before the decimal parts. E.g. "10" becomes "010", not "0010"

icd9GetValidDecimal: Returns subset of codes which are in valid decimal format, e.g. "100" or "V01.10"
icd9GetValidShort: Returns subset of codes which are in valid short format, e.g. "E800" or "41001"
icd9GetInvalid: Returns subset of codes which are not in valid short or decimal format.
icd9GetInvalidDecimal: Returns subset of codes which are not in valid decimal format.
icd9GetInvalidShort: Returns subset of codes which are not in valid short format.