R: Plot an Rpart Object

plot.rpart {rpart} | R Documentation

## Plot an Rpart Object

### Description

Plots an rpart object on the current graphics device.

### Usage

    ## S3 method for class 'rpart'
    plot(x, uniform = FALSE, branch = 1, compress = FALSE, nspace,
         margin = 0, minbranch = 0.3, ...)

### Arguments

`x` | a fitted object of class `"rpart"`, containing a classification, regression, or rate tree.
`uniform` | if `TRUE`, uniform vertical spacing of the nodes is used; this may be less cluttered when fitting a large plot onto a page. The default is to use a non-uniform spacing proportional to the error in the fit.
`branch` | controls the shape of the branches from parent to child node. Any number from 0 to 1 is allowed. A value of 1 gives square shouldered branches, a value of 0 give V shaped branches, with other values being intermediate.
`compress` | if `FALSE`, the leaf nodes will be at the horizontal plot coordinates of `1:nleaves`. If `TRUE`, the routine attempts a more compact arrangement of the tree. The compaction algorithm assumes `uniform=TRUE`; surprisingly, the result is usually an improvement even when that is not the case.
`nspace` | the amount of extra space between a node with children and a leaf, as compared to the minimal space between leaves. Applies to compressed trees only. The default is the value of `branch`.
`margin` | an extra fraction of white space to leave around the borders of the tree. (Long labels sometimes get cut off by the default computation).
`minbranch` | set the minimum length for a branch to `minbranch` times the average branch length. This parameter is ignored if `uniform=TRUE`. Sometimes a split will give very little improvement, or even (in the classification case) no improvement at all. A tree with branch lengths strictly proportional to improvement leaves no room to squeeze in node labels.
`...` | arguments to be passed to or from other methods.

### Details

This function is a method for the generic function `plot`, for objects of class `rpart`. The y-coordinate of the top node of the tree will always be 1.

### Value

The coordinates of the nodes are returned as a list, with components `x` and `y`.

### Side Effects

An unlabeled plot is produced on the current graphics device: one being opened if needed.

In order to build up a plot in the usual S style, e.g., a separate `text` command for adding labels, some extra information about the plot needs be retained. This is kept in an environment in the package.

### See Also

`rpart`, `text.rpart`

### Examples

    fit <- rpart(Price ~ Mileage + Type + Country, cu.summary)
    par(xpd = TRUE)
    plot(fit, compress = TRUE)
    text(fit, use.n = TRUE)

[Package rpart version 4.1-8 Index]