compact

Reduce size of machine learning model

Syntax

CompactMdl = compact(Mdl)

Description

CompactMdl = compact(Mdl) returns a compact model (CompactMdl), the compact version of the trained machine learning model Mdl.

CompactMdl does not contain the training data, whereas Mdl contains the training data in its X and Y properties. Therefore, although you can predict class labels using CompactMdl, you cannot perform tasks such as cross-validation with the compact model.

Examples

Reduce Size of Naive Bayes Classifier

Reduce the size of a full naive Bayes classifier by removing the training data. Full naive Bayes classifiers hold the training data. You can use a compact naive Bayes classifier to improve memory efficiency.

Load the ionosphere data set. Remove the first two predictors for stability.

load ionosphere
X = X(:,3:end);

Train a naive Bayes classifier using the predictors X and class labels Y. A recommended practice is to specify the class names. fitcnb assumes that each predictor is conditionally and normally distributed.

Mdl = fitcnb(X,Y,'ClassNames',{'b','g'})

Mdl = 
  ClassificationNaiveBayes
              ResponseName: 'Y'
     CategoricalPredictors: []
                ClassNames: {'b'  'g'}
            ScoreTransform: 'none'
           NumObservations: 351
         DistributionNames: {1×32 cell}
    DistributionParameters: {2×32 cell}


  Properties, Methods

Mdl is a trained ClassificationNaiveBayes classifier.

Reduce the size of the naive Bayes classifier.

CMdl = compact(Mdl)

CMdl = 
  CompactClassificationNaiveBayes
              ResponseName: 'Y'
     CategoricalPredictors: []
                ClassNames: {'b'  'g'}
            ScoreTransform: 'none'
         DistributionNames: {1×32 cell}
    DistributionParameters: {2×32 cell}


  Properties, Methods

CMdl is a trained CompactClassificationNaiveBayes classifier.

Display the amount of memory used by each classifier.

whos('Mdl','CMdl')

  Name      Size             Bytes  Class                                                        Attributes

  CMdl      1x1              16436  classreg.learning.classif.CompactClassificationNaiveBayes              
  Mdl       1x1             112598  ClassificationNaiveBayes                                               

The full naive Bayes classifier (Mdl) is more than seven times larger than the compact naive Bayes classifier (CMdl).

To label new observations efficiently, you can remove Mdl from the MATLAB® Workspace, and then pass CMdl and new predictor values to predict.

Reduce Size of SVM Classifier

Reduce the size of a full support vector machine (SVM) classifier by removing the training data. Full SVM classifiers (that is, ClassificationSVM classifiers) hold the training data. To improve efficiency, use a smaller classifier.

Load the ionosphere data set.

load ionosphere

Train an SVM classifier. Standardize the predictor data and specify the order of the classes.

SVMModel = fitcsvm(X,Y,'Standardize',true,...
    'ClassNames',{'b','g'})

SVMModel = 
  ClassificationSVM
             ResponseName: 'Y'
    CategoricalPredictors: []
               ClassNames: {'b'  'g'}
           ScoreTransform: 'none'
          NumObservations: 351
                    Alpha: [90×1 double]
                     Bias: -0.1343
         KernelParameters: [1×1 struct]
                       Mu: [0.8917 0 0.6413 0.0444 0.6011 0.1159 0.5501 0.1194 0.5118 0.1813 0.4762 0.1550 0.4008 0.0934 0.3442 0.0711 0.3819 -0.0036 0.3594 -0.0240 0.3367 0.0083 0.3625 -0.0574 0.3961 -0.0712 0.5416 -0.0695 0.3784 … ] (1×34 double)
                    Sigma: [0.3112 0 0.4977 0.4414 0.5199 0.4608 0.4927 0.5207 0.5071 0.4839 0.5635 0.4948 0.6222 0.4949 0.6528 0.4584 0.6180 0.4968 0.6263 0.5191 0.6098 0.5182 0.6038 0.5275 0.5785 0.5085 0.5162 0.5500 0.5759 0.5080 … ] (1×34 double)
           BoxConstraints: [351×1 double]
          ConvergenceInfo: [1×1 struct]
          IsSupportVector: [351×1 logical]
                   Solver: 'SMO'


  Properties, Methods

SVMModel is a ClassificationSVM classifier.

Reduce the size of the SVM classifier.

CompactSVMModel = compact(SVMModel)

CompactSVMModel = 
  CompactClassificationSVM
             ResponseName: 'Y'
    CategoricalPredictors: []
               ClassNames: {'b'  'g'}
           ScoreTransform: 'none'
                    Alpha: [90×1 double]
                     Bias: -0.1343
         KernelParameters: [1×1 struct]
                       Mu: [0.8917 0 0.6413 0.0444 0.6011 0.1159 0.5501 0.1194 0.5118 0.1813 0.4762 0.1550 0.4008 0.0934 0.3442 0.0711 0.3819 -0.0036 0.3594 -0.0240 0.3367 0.0083 0.3625 -0.0574 0.3961 -0.0712 0.5416 -0.0695 0.3784 … ] (1×34 double)
                    Sigma: [0.3112 0 0.4977 0.4414 0.5199 0.4608 0.4927 0.5207 0.5071 0.4839 0.5635 0.4948 0.6222 0.4949 0.6528 0.4584 0.6180 0.4968 0.6263 0.5191 0.6098 0.5182 0.6038 0.5275 0.5785 0.5085 0.5162 0.5500 0.5759 0.5080 … ] (1×34 double)
           SupportVectors: [90×34 double]
      SupportVectorLabels: [90×1 double]


  Properties, Methods

CompactSVMModel is a CompactClassificationSVM classifier.

Display the amount of memory used by each classifier.

whos('SVMModel','CompactSVMModel')

  Name                 Size             Bytes  Class                                                 Attributes

  CompactSVMModel      1x1              30749  classreg.learning.classif.CompactClassificationSVM              
  SVMModel             1x1             140279  ClassificationSVM                                               

The full SVM classifier (SVMModel) is more than four times larger than the compact SVM classifier (CompactSVMModel).

To label new observations efficiently, you can remove SVMModel from the MATLAB® Workspace, and then pass CompactSVMModel and new predictor values to predict.

To further reduce the size of the compact SVM classifier, use the discardSupportVectors function to discard support vectors.

Reduce Size of Generalized Additive Model

Reduce the size of a full generalized additive model (GAM) for regression by removing the training data. Full models hold the training data. You can use a compact model to improve memory efficiency.

Load the carbig data set.

load carbig

Specify Acceleration, Displacement, Horsepower, and Weight as the predictor variables (X) and MPG as the response variable (Y).

X = [Acceleration,Displacement,Horsepower,Weight];
Y = MPG;

Train a GAM using X and Y.

Mdl = fitrgam(X,Y)

Mdl = 
  RegressionGAM
              ResponseName: 'Y'
     CategoricalPredictors: []
         ResponseTransform: 'none'
                 Intercept: 26.9442
    IsStandardDeviationFit: 0
           NumObservations: 398


  Properties, Methods

Mdl is a RegressionGAM model object.

Reduce the size of the model.

CMdl = compact(Mdl)

CMdl = 
  CompactRegressionGAM
              ResponseName: 'Y'
     CategoricalPredictors: []
         ResponseTransform: 'none'
                 Intercept: 26.9442
    IsStandardDeviationFit: 0


  Properties, Methods

CMdl is a CompactRegressionGAM model object.

Display the amount of memory used by each regression model.

whos('Mdl','CMdl')

  Name      Size             Bytes  Class                                          Attributes

  CMdl      1x1             597222  classreg.learning.regr.CompactRegressionGAM              
  Mdl       1x1             631046  RegressionGAM                                            

The full model (Mdl) is larger than the compact model (CMdl).

To efficiently predict responses for new observations, you can remove Mdl from the MATLAB® Workspace, and then pass CMdl and new predictor values to predict.

Reduce Size of Quantile Linear Regression Model

Reduce the size of a full quantile linear regression model by removing the training data. Full quantile regression models include the training data. You can use a compact quantile regression model to improve memory efficiency.

Load the carbig data set, which contains measurements of cars made in the 1970s and early 1980s. Create a matrix X containing the predictor variables Acceleration, Displacement, Horsepower, and Weight. Store the response variable MPG in the variable Y.

load carbig
X = [Acceleration,Displacement,Horsepower,Weight];
Y = MPG;

Delete rows of X and Y where either array has missing values.

R = rmmissing([X Y]);
X = R(:,1:end-1);
Y = R(:,end);

Train a quantile linear regression model. Specify to use the 0.25, 0.50, and 0.75 quantiles (that is, the lower quartile, median, and upper quartile). To improve the model fit, change the beta tolerance to 1e-6 instead of the default value 1e-4, and use a ridge (L2) regularization term of 1.

Mdl = fitrqlinear(X,Y,Quantiles=[0.25,0.50,0.75], ...
    BetaTolerance=1e-6,Lambda=1)

Mdl = 
  RegressionQuantileLinear
             ResponseName: 'Y'
    CategoricalPredictors: []
        ResponseTransform: 'none'
                     Beta: [4×3 double]
                     Bias: [17.0306 22.5291 29.0044]
                Quantiles: [0.2500 0.5000 0.7500]


  Properties, Methods

Mdl is a RegressionQuantileLinear model object.

Reduce the size of the quantile regression model.

CompactMdl = compact(Mdl)

CompactMdl = 
  CompactRegressionQuantileLinear
             ResponseName: 'Y'
    CategoricalPredictors: []
        ResponseTransform: 'none'
                     Beta: [4×3 double]
                     Bias: [17.0306 22.5291 29.0044]
                Quantiles: [0.2500 0.5000 0.7500]


  Properties, Methods

CompactMdl is a CompactRegressionQuantileLinear model object.

Display the amount of memory used by each model.

whos("Mdl","CompactMdl")

  Name            Size            Bytes  Class                                                     Attributes

  CompactMdl      1x1              4936  classreg.learning.regr.CompactRegressionQuantileLinear              
  Mdl             1x1             26426  RegressionQuantileLinear                                            

The full quantile linear regression model (Mdl) is more than five times larger than the compact quantile linear regression model (CompactMdl).

To predict the response for new observations efficiently, you can remove Mdl from the MATLAB® Workspace, and then pass CompactMdl and new predictor values to predict.

Input Arguments

Mdl — Machine learning model

full classification model object | full regression model object | full quantile regression model

Machine learning model, specified as a full classification, regression, or quantile regression model object, as given in the following tables of supported models.

Classification Model Object

Model	Full Classification Model Object
Discriminant analysis classifier	ClassificationDiscriminant
Multiclass model for support vector machines or other classifiers	ClassificationECOC
Ensemble of learners for classification	ClassificationBaggedEnsemble, ClassificationEnsemble
Generalized additive model	ClassificationGAM
Naive Bayes model	ClassificationNaiveBayes
Neural network classifier	ClassificationNeuralNetwork
Support vector machine for one-class and binary classification	ClassificationSVM
Binary decision tree for multiclass classification	ClassificationTree

Regression Model Object

Model	Full Regression Model Object
Ensemble of regression models	RegressionBaggedEnsemble, RegressionEnsemble
Generalized additive model (GAM)	RegressionGAM
Gaussian process regression (GPR) model	RegressionGP
Neural network regression model	RegressionNeuralNetwork
Support vector machine for regression	RegressionSVM
Regression tree	RegressionTree

Quantile Regression Model Object

Model	Full Quantile Regression Model Object
Quantile linear regression model (since R2025a)	RegressionQuantileLinear
Quantile neural network model for regression (since R2025a)	RegressionQuantileNeuralNetwork

Output Arguments

CompactMdl — Compact machine learning model

compact classification model object | compact regression model object | compact quantile regression model object

Compact machine learning model, returned as one of the compact model objects in the following tables, depending on the input model Mdl.

Classification Model Object

Model	Full Model (Mdl)	Compact Model (CompactMdl)
Discriminant analysis classifier	ClassificationDiscriminant	CompactClassificationDiscriminant
Multiclass model for support vector machines or other classifiers	ClassificationECOC	CompactClassificationECOC
Ensemble of learners for classification	ClassificationBaggedEnsemble, ClassificationEnsemble	CompactClassificationEnsemble
Generalized additive model	ClassificationGAM	CompactClassificationGAM
Naive Bayes model	ClassificationNaiveBayes	CompactClassificationNaiveBayes
Neural network classifier	ClassificationNeuralNetwork	CompactClassificationNeuralNetwork
Support vector machine for one-class and binary classification	ClassificationSVM	CompactClassificationSVM
Binary decision tree for multiclass classification	ClassificationTree	CompactClassificationTree

Regression Model Object

Model	Full Model (Mdl)	Compact Model (CompactMdl)
Ensemble of regression models	RegressionBaggedEnsemble, RegressionEnsemble	CompactRegressionEnsemble
Generalized additive model	RegressionGAM	CompactRegressionGAM
Gaussian process regression (GPR) model	RegressionGP	CompactRegressionGP
Neural network regression model	RegressionNeuralNetwork	CompactRegressionNeuralNetwork
Support vector machine for regression	RegressionSVM	CompactRegressionSVM
Regression tree	RegressionTree	CompactRegressionTree

Quantile Regression Model Object

Model	Full Model (Mdl)	Compact Model (CompactMdl)
Quantile linear regression model (since R2025a)	RegressionQuantileLinear	CompactRegressionQuantileLinear
Quantile neural network model for regression (since R2025a)	RegressionQuantileNeuralNetwork	CompactRegressionQuantileNeuralNetwork

Extended Capabilities

GPU Arrays

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

Usage notes and limitations:

• This function fully supports GPU arrays for a trained classification model specified as a ClassificationBaggedEnsemble, ClassificationECOC, ClassificationEnsemble, ClassificationNeuralNetwork, ClassificationSVM, or ClassificationTree object.

• This function fully supports GPU arrays for a trained regression model specified as a RegressionBaggedEnsemble, RegressionEnsemble, RegressionNeuralNetwork, RegressionSVM, or RegressionTree object.

For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Version History

Introduced in R2011a

R2025a: Reduce size of quantile regression models

You can reduce the size of RegressionQuantileLinear and RegressionQuantileNeuralNetwork model objects by using the compact object function. The function returns CompactRegressionQuantileLinear and CompactRegressionQuantileNeuralNetwork model objects, respectively.

R2024b: Specify GPU arrays for neural network models (requires Parallel Computing Toolbox)

compact fully supports GPU arrays for RegressionNeuralNetwork and ClassificationNeuralNetwork models.

R2023a: Specify GPU arrays for regression SVM models (requires Parallel Computing Toolbox)

compact fully supports GPU arrays for RegressionSVM models.