# icd9DropLeadingZeroes: drop zero padding from decimal ICD-9 code. In icd9: Tools for Working with ICD-9 Codes, and Finding Comorbidities

## Description

decimal form ICD-9 codes are not ambiguous if the leading zeroes are dropped. Some short-form ICD-9 codes would not be ambiguous, e.g. "1" but many would be problematic. This is the inverse of `icd9AddLeadingZeroesDecimal`.

Invalid codes have no guaranteed result, and may give NA, or a (possibly valid) code in repsonse.

## Usage

 ```1 2 3 4 5 6 7``` ```icd9DropLeadingZeroes(icd9, isShort) icd9DropLeadingZeroesDecimal(icd9Decimal) icd9DropLeadingZeroesShort(icd9Short) icd9DropLeadingZeroesMajor(major) ```

## Arguments

 `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". `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"

## Value

character vector of ICD-9 codes with extra zeroes dropped from major part

Other ICD-9 convert: `icd9ChaptersToMap`, `icd9LongToWide`, `icd9PartsToShort`, `icd9WideToLong`