node.impurity: Internal Function to Calculate Impurity of Nodes
In oblique.tree: Oblique Trees for Classification Data

Description Usage Arguments Details Value Author(s) Examples

Calculates the impurity of a node.

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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) = ∑_{i!=j} p_i p_j = 1-∑_i p_i^2.

The “deviance” measure is calculated as

i(p) = -2 ∑_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")

Loading required package: tree
Loading required package: glmnet
Loading required package: Matrix
Loading required package: foreach
Loaded glmnet 2.0-12

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