Plot an Rpart Object

Plots an rpart object on the current graphics device.

# S3 method for 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.

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.

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.

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)