| node.impurity {oblique.tree} | R Documentation |
Calculates the impurity of a node.
node.impurity(
class.probabilities,
impurity.measure = c("deviance","gini"))
class.probabilities |
A vector of observed class probabilities. |
impurity.measure |
Impurity criterion to use. |
Where p_i are observed class probabilities, ``Gini Impurity'' is calculated as
i(p) = sum_{i!=j} p_i p_j = 1-sum_i p_i^2.
The ``deviance'' measure is calculated as
i(p) = -2 sum_i p_i log(p_i)
to allow for internal compatibility. Note: 0 log(0) = 0.
A value for node impurity is returned.
A. Truong
#A node only has observations of one type
oblique.tree:::node.impurity(
class.probabilities = c(1,0,0,0),
impurity.measure = "deviance")
#Another node has equal numbers of observations of each type
oblique.tree:::node.impurity(
class.probabilities = c(0.25,0.25,0.25,0.25),
impurity.measure = "deviance")