plotcp {rpart}  R Documentation 
Gives a visual representation of the crossvalidation results in an
rpart
object.
plotcp(x, minline = TRUE, lty = 3, col = 1, upper = c("size", "splits", "none"), ...)
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 
The set of possible costcomplexity 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 crossvalidation 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 crossvalidated
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.
None.
A plot is produced on the current graphical device.