R: Variables used in a random forest

varUsed {randomForest} | R Documentation

## Variables used in a random forest

### Description

Find out which predictor variables are actually used in the random forest.

### Usage

    varUsed(x, by.tree=FALSE, count=TRUE)

### Arguments

`x` | An object of class `randomForest`.
`by.tree` | Should the list of variables used be broken down by trees in the forest?
`count` | Should the frequencies that variables appear in trees be returned?

### Value

If `count=TRUE` and `by.tree=FALSE`, a integer vector containing frequencies that variables are used in the forest. If `by.tree=TRUE`, a matrix is returned, breaking down the counts by tree (each column corresponding to one tree and each row to a variable).

If `count=FALSE` and `by.tree=TRUE`, a list of integer indices is returned giving the variables used in the trees, else if `by.tree=FALSE`, a vector of integer indices giving the variables used in the entire forest.

### Author(s)

Andy Liaw

### See Also

`randomForest`

### Examples

    data(iris)
    set.seed(17)
    varUsed(randomForest(Species~., iris, ntree=100))

[Package randomForest version 4.6-14 Index]