# factor_: Fast Factor Generation In icd9: Tools for Working with ICD-9 Codes, and Finding Comorbidities

## Description

This function generates factors more quickly, by leveraging `fastmatch::fmatch`. The speed increase for ICD-9 codes is about 33

## Usage

 ```1 2 3``` ```factor_(x, levels = NULL, labels = levels, na.last = NA) factor_nosort(x, levels = NULL, labels = levels) ```

## Arguments

 `x` An object of atomic type `integer`, `numeric`, `character` or `logical`. `levels` An optional character vector of levels. Is coerced to the same type as `x`. By default, we compute the levels as `sort(unique.default(x))`. `labels` A set of labels used to rename the levels, if desired. `na.last` If `TRUE` and there are missing values, the last level is set as `NA`; otherwise; they are removed.

## Details

`NaN`s are converted to `NA` when used on numerics. Extracted from https://github.com/kevinushey/Kmisc.git

These feature from base R are missing: ```exclude = NA, ordered = is.ordered(x), nmax = NA```

I don't think there is any requirement for factor levels to be sorted in advance, especially not for ICD-9 codes where a simple alphanumeric sorting will likely be completely wrong.

## Author(s)

Kevin Ushey, adapted by Jack Wasey

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17``` ```## Not run: pts <- icd9:::randomUnorderedPatients(1e7) u <- unique.default(pts\$icd9) # this shows that stringr (which uses stringi) sort takes 50% longer than # built-in R sort. microbenchmark::microbenchmark(sort(u), stringr::str_sort(u)) # this shows that \code{factor_} is about 50% faster than \code{factor} for # big vectors of strings # without sorting is much faster: microbenchmark::microbenchmark(factor(pts\$icd9), factor_(pts\$icd9), factor_nosort(pts\$icd9), times=25) ## End(Not run) ```

icd9 documentation built on May 30, 2017, 2:25 a.m.