Sorts lists of numeric only, V or E codes. Note that a simple numeric sort does not work for ICD-9 codes, since "162" > "1620", and also V codes precede E codes.

1 2 3 4 5 | ```
icd9Sort(icd9, isShort = icd9GuessIsShort(icd9))
icd9SortShort(icd9Short)
icd9SortDecimal(icd9Decimal)
``` |

`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. |

`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" |

`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" |

Implementation used fast built-in sort, then shuffles the E codes to the end.

sorted vector of ICD-9 codes. Numeric, then E codes, then V codes.

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