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=T, 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
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
Side Effects
A plot is produced on the current graphical device.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.