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crossval

Class: RegressionTree

Cross-validated decision tree

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Syntax

cvmodel = crossval(model)
cvmodel = crossval(model,Name,Value)

Description

cvmodel = crossval(model) creates a partitioned model from model, a fitted regression tree. By default, crossval uses 10-fold cross validation on the training data to create cvmodel.

cvmodel = crossval(model,Name,Value) creates a partitioned model with additional options specified by one or more Name,Value pair arguments.

Input Arguments

model

A regression model, produced using fitrtree.

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

CVPartition

Object of class cvpartition, created by the cvpartition function. crossval splits the data into subsets with cvpartition.

Use only one of these four options at a time: 'KFold', 'Holdout', 'Leaveout', or 'CVPartition'.

Default: []

Holdout

Holdout validation tests the specified fraction of the data, and uses the rest of the data for training. Specify a numeric scalar from 0 to 1. You can only use one of these four options at a time for creating a cross-validated tree: 'KFold', 'Holdout', 'Leaveout', or 'CVPartition'.

KFold

Number of folds to use in a cross-validated tree, a positive integer value greater than 1.

Use only one of these four options at a time: 'KFold', 'Holdout', 'Leaveout', or 'CVPartition'.

Default: 10

Leaveout

Set to 'on' for leave-one-out cross-validation.

Output Arguments

cvmodel

A partitioned model of class RegressionPartitionedModel.

Examples

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Open Live Script

Load the carsmall data set. Consider Acceleration, Displacement, Horsepower, and Weight as predictor variables.

load carsmall
X = [Acceleration Displacement Horsepower Weight];

Grow a regression tree using the entire data set.

Mdl = fitrtree(X,MPG);

Mdl is a RegressionTree model.

Cross-validate the regression tree using 10-fold cross-validation.

CVMdl = crossval(Mdl);

CVMdl is a RegressionPartitionedModel cross-validated model. crossval stores the ten trained, compact regression trees in the Trained property of CVMdl.

Display the compact regression tree that crossval trained using all observations except those in the first fold.

CVMdl.Trained{1}
ans = 
  CompactRegressionTree
           PredictorNames: {'x1'  'x2'  'x3'  'x4'}
             ResponseName: 'Y'
    CategoricalPredictors: []
        ResponseTransform: 'none'


  Properties, Methods

Estimate the generalization error of Mdl by computing the 10-fold cross-validated mean-squared error.

L = kfoldLoss(CVMdl)
L = 23.5706

Tips

  • Assess the predictive performance of model on cross-validated data using the “kfold” methods and properties of cvmodel, such as kfoldLoss.

Alternatives

You can create a cross-validation tree directly from the data, instead of creating a decision tree followed by a cross-validation tree. To do so, include one of these five options in fitrtree: 'CrossVal', 'KFold', 'Holdout', 'Leaveout', or 'CVPartition'.

Extended Capabilities

See Also

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