resubMargin

Class: ClassificationTree

Classification margins by resubstitution

Syntax

M = resubMargin(tree)


Description

M = resubMargin(tree) returns resubstitution classification margins for tree.

Input Arguments

tree	A classification tree created by fitctree.

Output Arguments

M	A numeric column-vector of length size(tree.X,1) containing the classification margins.

Examples

Find the margins for a classification tree for the Fisher iris data by resubstitution. Examine several entries:

load fisheriris
tree = fitctree(meas,species);
M = resubMargin(tree);
M(1:25:end)

ans =
    1.0000
    1.0000
    1.0000
    1.0000
    0.9565
    0.9565

More About

Margin

Classification margin is the difference between classification score for the true class and maximal classification score for the false classes. A high value of margin indicates a more reliable prediction than a low value.

Score (tree)

For trees, the score of a classification of a leaf node is the posterior probability of the classification at that node. The posterior probability of the classification at a node is the number of training sequences that lead to that node with the classification, divided by the number of training sequences that lead to that node.

For an example, see Posterior Probability Definition for Classification Tree.

Extended Capabilities

GPU Arrays

Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.

This function fully supports GPU arrays. For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).