resubMargin

Resubstitution classification margins for classification tree model

Syntax

m = resubMargin(tree)

Description

m = resubMargin(tree) returns the resubstitution classification margins m for the trained classification tree model tree using the training data stored in tree.X and the corresponding true class labels stored in tree.Y. m is returned as a numeric column vector with the same length as tree.Y. The software estimates each entry of m using the trained classification tree model tree, the corresponding row of tree.X, and the true class label tree.Y.

Examples

Find Margins for Classification Tree by Resubstitution

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

Input Arguments

tree — Classification tree model

ClassificationTree model object

Classification tree model, specified as a ClassificationTree model object trained with fitctree.

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).

Version History

Introduced in R2011a