Plot an Rpart Object

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=.3, bar,...)

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 horzontal 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 percentage 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.
bar: length of bar at root (default = 0.03) – used instead of char "|"
...: arguments to be passed to or from other methods.

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.

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.

Examples

data(car.test.frame)
fit <- rpart(Price ~ Mileage + Type + Country, car.test.frame)
plot(fit, compress=TRUE)
text(fit, use.n=TRUE)