Show all possible pruned subtrees
prune.seq(tree, eps = 0.01, plot.it = TRUE)a named list of two items:
thr a set of threshold values that sequentially reduce tree size
nodes the corresponding tree sizes (number of terminal nodes)
a tree model object output from contrast
small increment defining grid of threshold values
a logical flag indicating plot/don't plot of number of nodes versus threshold value for all pruned subtrees, default TRUE