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predict

Classify observations using ensemble of classification models

Syntax

labels = predict(Mdl,X)
labels = predict(Mdl,X,Name,Value)
[labels,score] = predict(___)

Description

labels = predict(Mdl,X) returns a vector of predicted class labels for the predictor data in the table or matrix X, based on the full or compact, trained classification ensemble Mdl.

labels = predict(Mdl,X,Name,Value) uses additional options specified by one or more Name,Value pair arguments.

[labels,score] = predict(___) also returns a matrix of classification scores (score), indicating the likelihood that a label comes from a particular class, using any of the input arguments in the previous syntaxes. For each observation in X, the predicted class label corresponds to the maximum score among all classes.

Input Arguments

Mdl

A classification ensemble created by fitcensemble or a compact classification ensemble created by compact.

X

Predictor data to be classified, specified as a numeric matrix or table.

Each row of X corresponds to one observation, and each column corresponds to one variable.

  • For a numeric matrix:

    • The variables making up the columns of X must have the same order as the predictor variables that trained Mdl.

    • If you trained Mdl using a table (for example, Tbl), then X can be a numeric matrix if Tbl contains all numeric predictor variables. To treat numeric predictors in Tbl as categorical during training, identify categorical predictors using the CategoricalPredictors name-value pair argument of fitcensemble. If Tbl contains heterogeneous predictor variables (for example, numeric and categorical data types) and X is a numeric matrix, then predict throws an error.

  • For a table:

    • predict does not support multi-column variables and cell arrays other than cell arrays of character vectors.

    • If you trained Mdl using a table (for example, Tbl), then all predictor variables in X must have the same variable names and be of the same data types as those that trained Mdl (stored in Mdl.PredictorNames). However, the column order of X does not need to correspond to the column order of Tbl. Tbl and X can contain additional variables (response variables, observation weights, etc.), but predict ignores them.

    • If you trained Mdl using a numeric matrix, then the predictor names in Mdl.PredictorNames and corresponding predictor variable names in X must be the same. To specify predictor names during training, see the PredictorNames name-value pair argument of fitcensemble. All predictor variables in X must be numeric vectors. X can contain additional variables (response variables, observation weights, etc.), but predict ignores them.

Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside quotes. You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

'Learners'

Indices of weak learners predict uses for computation of responses, a numeric vector.

Default: 1:T, where T is the number of weak learners in Mdl

'UseObsForLearner'

A logical matrix of size N-by-T, where:

  • N is the number of rows of X.

  • T is the number of weak learners in Mdl.

When UseObsForLearner(i,j) is true, learner j is used in predicting the class of row i of X.

Default: true(N,T)

Output Arguments

labels

Vector of classification labels. labels has the same data type as the labels used in training Mdl. (The software treats string arrays as cell arrays of character vectors.)

score

A matrix with one row per observation and one column per class. For each observation and each class, the score generated by each tree is the probability of this observation originating from this class computed as the fraction of observations of this class in a tree leaf. predict averages these scores over all trees in the ensemble.

Examples

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Load Fisher's iris data set. Determine the sample size.

load fisheriris
N = size(meas,1);

Partition the data into training and test sets. Hold out 10% of the data for testing.

rng(1); % For reproducibility
cvp = cvpartition(N,'Holdout',0.1);
idxTrn = training(cvp); % Training set indices
idxTest = test(cvp);    % Test set indices

Store the training data in a table.

tblTrn = array2table(meas(idxTrn,:));
tblTrn.Y = species(idxTrn);

Train a classification ensemble using AdaBoostM2 and the training set. Specify tree stumps as the weak learners.

t = templateTree('MaxNumSplits',1);
Mdl = fitcensemble(tblTrn,'Y','Method','AdaBoostM2','Learners',t);

Predict labels for the test set. You trained model using a table of data, but you can predict labels using a matrix.

labels = predict(Mdl,meas(idxTest,:));

Construct a confusion matrix for the test set.

confusionchart(species(idxTest),labels);

Mdl misclassifies one versicolor iris as virginica in the test set.

More About

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Extended Capabilities

Introduced in R2011a