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.

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

`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" |

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

Other ICD-9 convert: `icd9ChaptersToMap`

,
`icd9LongToWide`

,
`icd9PartsToShort`

,
`icd9WideToLong`

Questions? Problems? Suggestions? Tweet to @rdrrHQ or email at ian@mutexlabs.com.

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