310 ◾ Kweku-Muata Osei-Bryson
to us that for dierent end users and dierent DT problem instances, there may be
dierent value functions that map the number of leaves to this simplicity measure.
We assume that such a value function could have a continuous, concave piecewise
linear representation. Let F be the set of leaves in the DT, we assume simplicity
SIMPL
Leaf
=f
Leaf
(|F|), where f
Leaf
(|F|) is a concave piecewise linear function (e.g.,
trapezoidal) such that SIMPL
Leaf
∈(0, 1], with higher values of SIMPL
Leaf
indicat-
ing higher simplicity.
Simplicity Based on Average Chain Length (SIMPL
Rule
)
For a given rule, its length (i.e., number of predictor variables) provides a measure of
the complexity of the rule. erefore, another simplicity measure ...