Takes a fitted tree object and returns an object with the terminal nodes
reordered according to the increasing values of
x.
USAGE:
order.tree(tree, x)
REQUIRED ARGUMENTS:
tree
fitted model object of class
tree. This is assumed to
be the result of some function that produces an object
with the same named components as that returned by the
tree() function.
x
variable to reorder.
VALUE:
Tree object similar to
tree but with the terminal nodes reordered
according to increasing values of
x. Exact (global) reordering is not
generally possible; local reordering is such that at each internal
(parent) node, the mean of x at the left-sibling node is less than that
of it's right-sibling. The statistical properties
of the tree remain unchanged (eg. predictions/ goodness-of-fit).
[The physical concept is that a binary tree is actually a mobile in 3-D;
order.tree()
merely provides alternative rotations of the mobile components.]
SEE ALSO:
.
EXAMPLES:
z.cu <- tree(cu.summary)
# reorder nodes so that leftmost nodes contain inexpensive cars
# and rightmost nodes the expensive cars
newz.cu <- order.tree(z.cu, Price)