kawther hassine asked . 2022-07-14

TreeBagger parameter tuning for classification

How can I tune parameters for TreeBagger model for classification, I followed the example:"Tune Random Forest Using Quantile Error and Bayesian Optimization", https://fr.mathworks.com/help/stats/tune-random-forest-using-quantile-error-and-bayesian-optimization.html I only changed "regression" with "classification". The following code generated multiple errors:

results = bayesopt(@(params)oobErrRF(params,X),hyperparametersRF,...
    'AcquisitionFunctionName','expected-improvement-plus','Verbose',0);

errors:

Error using classreg.learning.internal.table2FitMatrix>resolveName (line 232)
One or more 'ResponseName' parameter values are invalid.

Error in classreg.learning.internal.table2FitMatrix (line 77)
        ResponseName = resolveName('ResponseName',ResponseName,FormulaResponseName,false,VarNames);

Error in ClassificationTree.prepareData (line 557)
            [X,Y,vrange,wastable,varargin] =
            classreg.learning.internal.table2FitMatrix(X,Y,varargin{:},'OrdinalIsCategorical',false);

Error in TreeBagger/init (line 1335)
                    ClassificationTree.prepareData(x,y,...

Error in TreeBagger (line 615)
            bagger = init(bagger,X,Y,makeArgs{:});

Error in oobErrRF2 (line 16)
randomForest = TreeBagger(300,X,'MPG','Method','classification',...

Error in @(params)oobErrRF2(params,trainingDataFeatures)

Error in BayesianOptimization/callObjNormally (line 2184)
                        Objective = this.ObjectiveFcn(conditionalizeX(this, X));

Error in BayesianOptimization/callObjFcn (line 2145)
                    = callObjNormally(this, X);

Error in BayesianOptimization/callObjFcn (line 2162)
                            = callObjFcn(this, X);

Error in BayesianOptimization/performFcnEval (line 2128)
                ObjectiveFcnObjectiveEvaluationTime, this] = callObjFcn(this, this.XNext);

Error in BayesianOptimization/run (line 1836)
                this = performFcnEval(this);

Error in BayesianOptimization (line 450)
            this = run(this);

Error in bayesopt (line 287)
Results = BayesianOptimization(Options);

would like to know if there is a way to use this method of tuning for classification. If not, how can I tune my parameters for a TreeBagger classifier.

parameter tuning , treebagger , classification , AI, Data Science, and Statistics , Statistics and

Expert Answer

Prashant Kumar answered . 2024-12-22 12:51:09

The following works for me in R2018a. It predicts 'Cylinders' (3 classes) and it calls oobError to get the misclassification rate of the ensemble.

load carsmall
Cylinders = categorical(Cylinders);
Mfg = categorical(cellstr(Mfg));
Model_Year = categorical(Model_Year);
X = table(Acceleration,Cylinders,Displacement,Horsepower,Mfg,...
    Model_Year,Weight,MPG);
rng('default'); % For reproducibility

maxMinLS = 20;
minLS = optimizableVariable('minLS',[1,maxMinLS],'Type','integer');
numPTS = optimizableVariable('numPTS',[1,size(X,2)-1],'Type','integer');
hyperparametersRF = [minLS; numPTS];

results = bayesopt(@(params)oobErrRF(params,X),hyperparametersRF,...
    'AcquisitionFunctionName','expected-improvement-plus','Verbose',1);

bestOOBErr = results.MinObjective
bestHyperparameters = results.XAtMinObjective

Mdl = TreeBagger(300,X,'Cylinders','Method','classification',...
    'MinLeafSize',bestHyperparameters.minLS,...
    'NumPredictorstoSample',bestHyperparameters.numPTS);

function oobErr = oobErrRF(params,X)
%oobErrRF Trains random forest and estimates out-of-bag quantile error
%   oobErr trains a random forest of 300 regression trees using the
%   predictor data in X and the parameter specification in params, and then
%   returns the out-of-bag quantile error based on the median. X is a table
%   and params is an array of OptimizableVariable objects corresponding to
%   the minimum leaf size and number of predictors to sample at each node.
randomForest = TreeBagger(300,X,'Cylinders','Method','classification',...
    'OOBPrediction','on','MinLeafSize',params.minLS,...
    'NumPredictorstoSample',params.numPTS);
oobErr = oobError(randomForest, 'Mode','ensemble');
end

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