R: Remove unused levels

rm.unused.levels {questionr} | R Documentation

## Remove unused levels

### Description

This function removes unused levels of a factor or in a data.frame. See examples.

### Usage

    rm.unused.levels(x, v = NULL)

### Arguments

`x` | a factor or a data frame
`v` | a list of variables (optional, if `x` is a data frame)

### Details

If `x` is a data frame, only factor variables of `x` will be impacted. If a list of variables is provided through `v`, only the unused levels of the specified variables will be removed.

### Author(s)

Joseph Larmarange <joseph@larmarange.net>

### Examples

    df <- data.frame(v1=c("a","b","a","b"),v2=c("x","x","y","y"))
    df$v1 <- factor(df$v1,c("a","b","c"))
    df$v2 <- factor(df$v2,c("x","y","z"))
    df
    str(df)
    str(rm.unused.levels(df))
    str(rm.unused.levels(df,"v1"))

[Package questionr version 0.6.3 Index]