plotcp Plot a Complexity Parameter Table for an Rpart Fit

Description

Gives a visual representation of the cross-validation results in an rpart object.

Usage

plotcp(x, minline = TRUE, lty = 3, col = 1,
       upper = c("size", "splits", "none"), ...)

Arguments

x	an object of class "rpart"
minline	whether a horizontal line is drawn 1SE above the minimum of the curve.
lty	line type for this line
col	colour for this line
upper	what is plotted on the top axis: the size of the tree (the number of leaves), the number of splits or nothing.
...	additional plotting parameters

Details

The set of possible cost-complexity prunings of a tree from a nested set. For the geometric means of the intervals of values of cp for which a pruning is optimal, a cross-validation has (usually) been done in the initial construction by rpart. The cptable in the fit contains the mean and standard deviation of the errors in the cross-validated prediction against each of the geometric means, and these are plotted by this function. A good choice of cp for pruning is often the leftmost value for which the mean lies below the horizontal line.

Value

None.

Side Effects

A plot is produced on the current graphical device.

See Also

rpart, printcp, rpart.object