ClassificationKernel

Gaussian kernel classification model using random feature expansion

Description

ClassificationKernel is a trained model object for a binary Gaussian kernel classification model using random feature expansion. ClassificationKernel is more practical for big data applications that have large training sets but can also be applied to smaller data sets that fit in memory.

Unlike other classification models, and for economical memory usage, ClassificationKernel model objects do not store the training data. However, they do store information such as the number of dimensions of the expanded space, the kernel scale parameter, prior-class probabilities, and the regularization strength.

You can use trained ClassificationKernel models to continue training using the training data and to predict labels or classification scores for new data. For details, see resume and predict.

Creation

Create a ClassificationKernel object using the fitckernel function. This function maps data in a low-dimensional space into a high-dimensional space, then fits a linear model in the high-dimensional space by minimizing the regularized objective function. The linear model in the high-dimensional space is equivalent to the model with a Gaussian kernel in the low-dimensional space. Available linear classification models include regularized support vector machine (SVM) and logistic regression models.

Properties

expand all

Kernel Classification Properties

`Learner` — Linear classification model type
`'logistic'` | `'svm'`

Linear classification model type, specified as 'logistic' or 'svm'.

In the following table, $f (x) = T (x) β + b .$

x is an observation (row vector) from p predictor variables.
$T (\cdot)$ is a transformation of an observation (row vector) for feature expansion. T(x) maps x in $ℝ^{p}$ to a high-dimensional space ( $ℝ^{m}$ ).
β is a vector of coefficients.
b is the scalar bias.

Value	Algorithm	Loss Function	`FittedLoss` Value
`'svm'`	Support vector machine	Hinge: $ℓ [y, f (x)] = \max [0, 1 - y f (x)]$	`'hinge'`
`'logistic'`	Logistic regression	Deviance (logistic): $ℓ [y, f (x)] = \log {1 + \exp [- y f (x)]}$	`'logit'`

`NumExpansionDimensions` — Number of dimensions of expanded space
positive integer

Number of dimensions of the expanded space, specified as a positive integer.

Data Types: single | double

`KernelScale` — Kernel scale parameter
positive scalar

Kernel scale parameter, specified as a positive scalar.

Data Types: char | single | double

`BoxConstraint` — Box constraint
positive scalar

Box constraint, specified as a positive scalar.

Data Types: double | single

`Lambda` — Regularization term strength
nonnegative scalar

Regularization term strength, specified as a nonnegative scalar.

Data Types: single | double

`Mu` — Predictor means
numeric vector | `[]`

Since R2023b

This property is read-only.

Predictor means, specified as a numeric vector. If you specify Standardize as 1 or true when you train the kernel model, then the length of the Mu vector is equal to the number of expanded predictors (see ExpandedPredictorNames). The vector contains 0 values for dummy variables corresponding to expanded categorical predictors.

If you set Standardize to 0 or false when you train the kernel model, then the Mu value is an empty vector ([]).

Data Types: double

`Sigma` — Predictor standard deviations
numeric vector | `[]`

Since R2023b

This property is read-only.

Predictor standard deviations, specified as a numeric vector. If you specify Standardize as 1 or true when you train the kernel model, then the length of the Sigma vector is equal to the number of expanded predictors (see ExpandedPredictorNames). The vector contains 1 values for dummy variables corresponding to expanded categorical predictors.

If you set Standardize to 0 or false when you train the kernel model, then the Sigma value is an empty vector ([]).

Data Types: double

`FittedLoss` — Loss function used to fit linear model
`'hinge'` | `'logit'`

This property is read-only.

Loss function used to fit the linear model, specified as 'hinge' or 'logit'.

Value	Algorithm	Loss Function	`Learner` Value
`'hinge'`	Support vector machine	Hinge: $ℓ [y, f (x)] = \max [0, 1 - y f (x)]$	`'svm'`
`'logit'`	Logistic regression	Deviance (logistic): $ℓ [y, f (x)] = \log {1 + \exp [- y f (x)]}$	`'logistic'`

`Regularization` — Complexity penalty type
`'ridge (L2)'`

Complexity penalty type, which is always 'ridge (L2)'.

The software composes the objective function for minimization from the sum of the average loss function (see FittedLoss) and the regularization term, ridge (L₂) penalty.

The ridge (L₂) penalty is

$\frac{λ}{2} \sum_{j = 1}^{p} β_{j}^{2}$

where λ specifies the regularization term strength (see Lambda). The software excludes the bias term (β₀) from the regularization penalty.

Other Classification Properties

`CategoricalPredictors` — Indices of categorical predictors
vector of positive integers | `[]`

Categorical predictor indices, specified as a vector of positive integers. CategoricalPredictors contains index values indicating that the corresponding predictors are categorical. The index values are between 1 and p, where p is the number of predictors used to train the model. If none of the predictors are categorical, then this property is empty ([]).

Data Types: single | double

`ClassNames` — Unique class labels
categorical array | character array | logical vector | numeric vector | cell array of character vectors

This property is read-only.

Unique class labels used in training, specified as a categorical or character array, logical or numeric vector, or cell array of character vectors. ClassNames has the same data type as the class labels Y. (The software treats string arrays as cell arrays of character vectors.) ClassNames also determines the class order.

`Cost` — Misclassification costs
square numeric matrix

This property is read-only.

Misclassification costs, specified as a square numeric matrix. Cost has K rows and columns, where K is the number of classes.

Cost(i,j) is the cost of classifying a point into class j if its true class is i. The order of the rows and columns of Cost corresponds to the order of the classes in ClassNames.

Data Types: double

`ModelParameters` — Parameters used for training model
structure

Parameters used for training the ClassificationKernel model, specified as a structure.

Access fields of ModelParameters using dot notation. For example, access the relative tolerance on the linear coefficients and the bias term by using Mdl.ModelParameters.BetaTolerance.

Data Types: struct

`PredictorNames` — Predictor names
cell array of character vectors

Predictor names in order of their appearance in the predictor data, specified as a cell array of character vectors. The length of PredictorNames is equal to the number of columns used as predictor variables in the training data X or Tbl.

Data Types: cell

`ExpandedPredictorNames` — Expanded predictor names
cell array of character vectors

Expanded predictor names, specified as a cell array of character vectors.

If the model uses encoding for categorical variables, then ExpandedPredictorNames includes the names that describe the expanded variables. Otherwise, ExpandedPredictorNames is the same as PredictorNames.

Data Types: cell

`Prior` — Prior class probabilities
numeric vector

This property is read-only.

Prior class probabilities, specified as a numeric vector. Prior has as many elements as classes in ClassNames, and the order of the elements corresponds to the elements of ClassNames.

Data Types: double

`ResponseName` — Response variable name
character vector

Response variable name, specified as a character vector.

Data Types: char

`ScoreTransform` — Score transformation function to apply to predicted scores
`'doublelogit'` | `'invlogit'` | `'ismax'` | `'logit'` | `'none'` | function handle | ...

Score transformation function to apply to predicted scores, specified as a function name or function handle.

For kernel classification models and before the score transformation, the predicted classification score for the observation x (row vector) is $f (x) = T (x) β + b .$

$T (\cdot)$ is a transformation of an observation for feature expansion.
β is the estimated column vector of coefficients.
b is the estimated scalar bias.

To change the score transformation function to function, for example, use dot notation.

For a built-in function, enter this code and replace function with a value from the table.

Mdl.ScoreTransform = 'function';

Value	Description
`"doublelogit"`	1/(1 + e^–2x)
`"invlogit"`	log(x / (1 – x))
`"ismax"`	Sets the score for the class with the largest score to 1, and sets the scores for all other classes to 0
`"logit"`	1/(1 + e^–x)
`"none"` or `"identity"`	x (no transformation)
`"sign"`	–1 for x < 0 0 for x = 0 1 for x > 0
`"symmetric"`	2x – 1
`"symmetricismax"`	Sets the score for the class with the largest score to 1, and sets the scores for all other classes to –1
`"symmetriclogit"`	2/(1 + e^–x) – 1

For a MATLAB^® function, or a function that you define, enter its function handle.
```
Mdl.ScoreTransform = @function;
```
function must accept a matrix of the original scores for each class, and then return a matrix of the same size representing the transformed scores for each class.

Data Types: char | function_handle

Object Functions

`edge`	Classification edge for Gaussian kernel classification model
`incrementalLearner`	Convert kernel model for binary classification to incremental learner
`lime`	Local interpretable model-agnostic explanations (LIME)
`loss`	Classification loss for Gaussian kernel classification model
`margin`	Classification margins for Gaussian kernel classification model
`partialDependence`	Compute partial dependence
`plotPartialDependence`	Create partial dependence plot (PDP) and individual conditional expectation (ICE) plots
`predict`	Predict labels for Gaussian kernel classification model
`resume`	Resume training of Gaussian kernel classification model
`shapley`	Shapley values

Examples

collapse all

Train Kernel Classification Model

Open Live Script

Train a binary kernel classification model using SVM.

Load the ionosphere data set. This data set has 34 predictors and 351 binary responses for radar returns, either bad ('b') or good ('g').

load ionosphere
[n,p] = size(X)

n = 
351

p = 
34

resp = unique(Y)

resp = 2x1 cell
    {'b'}
    {'g'}

Train a binary kernel classification model that identifies whether the radar return is bad ('b') or good ('g'). Extract a fit summary to determine how well the optimization algorithm fits the model to the data.

rng('default') % For reproducibility
[Mdl,FitInfo] = fitckernel(X,Y)

Mdl = 
  ClassificationKernel
              ResponseName: 'Y'
                ClassNames: {'b'  'g'}
                   Learner: 'svm'
    NumExpansionDimensions: 2048
               KernelScale: 1
                    Lambda: 0.0028
             BoxConstraint: 1

FitInfo = struct with fields:
                  Solver: 'LBFGS-fast'
            LossFunction: 'hinge'
                  Lambda: 0.0028
           BetaTolerance: 1.0000e-04
       GradientTolerance: 1.0000e-06
          ObjectiveValue: 0.2604
       GradientMagnitude: 0.0028
    RelativeChangeInBeta: 8.2512e-05
                 FitTime: 0.1059
                 History: []

Mdl is a ClassificationKernel model. To inspect the in-sample classification error, you can pass Mdl and the training data or new data to the loss function. Or, you can pass Mdl and new predictor data to the predict function to predict class labels for new observations. You can also pass Mdl and the training data to the resume function to continue training.

FitInfo is a structure array containing optimization information. Use FitInfo to determine whether optimization termination measurements are satisfactory.

For better accuracy, you can increase the maximum number of optimization iterations ('IterationLimit') and decrease the tolerance values ('BetaTolerance' and 'GradientTolerance') by using the name-value pair arguments. Doing so can improve measures like ObjectiveValue and RelativeChangeInBeta in FitInfo. You can also optimize model parameters by using the 'OptimizeHyperparameters' name-value pair argument.

Predict Class Labels and Resume Training

Open Live Script

Load the ionosphere data set. This data set has 34 predictors and 351 binary responses for radar returns, either bad ('b') or good ('g').

load ionosphere

Partition the data set into training and test sets. Specify a 20% holdout sample for the test set.

rng('default') % For reproducibility
Partition = cvpartition(Y,'Holdout',0.20);
trainingInds = training(Partition); % Indices for the training set
XTrain = X(trainingInds,:);
YTrain = Y(trainingInds);
testInds = test(Partition); % Indices for the test set
XTest = X(testInds,:);
YTest = Y(testInds);

Train a binary kernel classification model that identifies whether the radar return is bad ('b') or good ('g').

Mdl = fitckernel(XTrain,YTrain,'IterationLimit',5,'Verbose',1);

|=================================================================================================================|
| Solver |  Pass  |   Iteration  |   Objective   |     Step      |    Gradient   |    Relative    |  sum(beta~=0) |
|        |        |              |               |               |   magnitude   | change in Beta |               |
|=================================================================================================================|
|  LBFGS |      1 |            0 |  1.000000e+00 |  0.000000e+00 |  2.811388e-01 |                |             0 |
|  LBFGS |      1 |            1 |  7.585395e-01 |  4.000000e+00 |  3.594306e-01 |   1.000000e+00 |          2048 |
|  LBFGS |      1 |            2 |  7.160994e-01 |  1.000000e+00 |  2.028470e-01 |   6.923988e-01 |          2048 |
|  LBFGS |      1 |            3 |  6.825272e-01 |  1.000000e+00 |  2.846975e-02 |   2.388909e-01 |          2048 |
|  LBFGS |      1 |            4 |  6.699435e-01 |  1.000000e+00 |  1.779359e-02 |   1.325304e-01 |          2048 |
|  LBFGS |      1 |            5 |  6.535619e-01 |  1.000000e+00 |  2.669039e-01 |   4.112952e-01 |          2048 |
|=================================================================================================================|

Mdl is a ClassificationKernel model.

Predict the test-set labels, construct a confusion matrix for the test set, and estimate the classification error for the test set.

label = predict(Mdl,XTest);
ConfusionTest = confusionchart(YTest,label);

Figure contains an object of type ConfusionMatrixChart.

L = loss(Mdl,XTest,YTest)

L = 
0.3594

Mdl misclassifies all bad radar returns as good returns.

Continue training by using resume. This function continues training with the same options used for training Mdl.

UpdatedMdl = resume(Mdl,XTrain,YTrain);

|=================================================================================================================|
| Solver |  Pass  |   Iteration  |   Objective   |     Step      |    Gradient   |    Relative    |  sum(beta~=0) |
|        |        |              |               |               |   magnitude   | change in Beta |               |
|=================================================================================================================|
|  LBFGS |      1 |            0 |  6.535619e-01 |  0.000000e+00 |  2.669039e-01 |                |          2048 |
|  LBFGS |      1 |            1 |  6.132547e-01 |  1.000000e+00 |  6.355537e-03 |   1.522092e-01 |          2048 |
|  LBFGS |      1 |            2 |  5.938316e-01 |  4.000000e+00 |  3.202847e-02 |   1.498036e-01 |          2048 |
|  LBFGS |      1 |            3 |  4.169274e-01 |  1.000000e+00 |  1.530249e-01 |   7.234253e-01 |          2048 |
|  LBFGS |      1 |            4 |  3.679212e-01 |  5.000000e-01 |  2.740214e-01 |   2.495886e-01 |          2048 |
|  LBFGS |      1 |            5 |  3.332261e-01 |  1.000000e+00 |  1.423488e-02 |   9.558680e-02 |          2048 |
|  LBFGS |      1 |            6 |  3.235335e-01 |  1.000000e+00 |  7.117438e-03 |   7.137260e-02 |          2048 |
|  LBFGS |      1 |            7 |  3.112331e-01 |  1.000000e+00 |  6.049822e-02 |   1.252157e-01 |          2048 |
|  LBFGS |      1 |            8 |  2.972144e-01 |  1.000000e+00 |  7.117438e-03 |   5.796240e-02 |          2048 |
|  LBFGS |      1 |            9 |  2.837450e-01 |  1.000000e+00 |  8.185053e-02 |   1.484733e-01 |          2048 |
|  LBFGS |      1 |           10 |  2.797642e-01 |  1.000000e+00 |  3.558719e-02 |   5.856842e-02 |          2048 |
|  LBFGS |      1 |           11 |  2.771280e-01 |  1.000000e+00 |  2.846975e-02 |   2.349433e-02 |          2048 |
|  LBFGS |      1 |           12 |  2.741570e-01 |  1.000000e+00 |  3.914591e-02 |   3.113194e-02 |          2048 |
|  LBFGS |      1 |           13 |  2.725701e-01 |  5.000000e-01 |  1.067616e-01 |   8.729821e-02 |          2048 |
|  LBFGS |      1 |           14 |  2.667147e-01 |  1.000000e+00 |  3.914591e-02 |   3.491723e-02 |          2048 |
|  LBFGS |      1 |           15 |  2.621152e-01 |  1.000000e+00 |  7.117438e-03 |   5.104726e-02 |          2048 |
|  LBFGS |      1 |           16 |  2.601652e-01 |  1.000000e+00 |  3.558719e-02 |   3.764904e-02 |          2048 |
|  LBFGS |      1 |           17 |  2.589052e-01 |  1.000000e+00 |  3.202847e-02 |   3.655744e-02 |          2048 |
|  LBFGS |      1 |           18 |  2.583185e-01 |  1.000000e+00 |  7.117438e-03 |   6.490571e-02 |          2048 |
|  LBFGS |      1 |           19 |  2.556482e-01 |  1.000000e+00 |  9.252669e-02 |   4.601390e-02 |          2048 |
|  LBFGS |      1 |           20 |  2.542643e-01 |  1.000000e+00 |  7.117438e-02 |   4.141838e-02 |          2048 |
|=================================================================================================================|
| Solver |  Pass  |   Iteration  |   Objective   |     Step      |    Gradient   |    Relative    |  sum(beta~=0) |
|        |        |              |               |               |   magnitude   | change in Beta |               |
|=================================================================================================================|
|  LBFGS |      1 |           21 |  2.532117e-01 |  1.000000e+00 |  1.067616e-02 |   1.661720e-02 |          2048 |
|  LBFGS |      1 |           22 |  2.529890e-01 |  1.000000e+00 |  2.135231e-02 |   1.231678e-02 |          2048 |
|  LBFGS |      1 |           23 |  2.523232e-01 |  1.000000e+00 |  3.202847e-02 |   1.958586e-02 |          2048 |
|  LBFGS |      1 |           24 |  2.506736e-01 |  1.000000e+00 |  1.779359e-02 |   2.474613e-02 |          2048 |
|  LBFGS |      1 |           25 |  2.501995e-01 |  1.000000e+00 |  1.779359e-02 |   2.514352e-02 |          2048 |
|  LBFGS |      1 |           26 |  2.488242e-01 |  1.000000e+00 |  3.558719e-03 |   1.531810e-02 |          2048 |
|  LBFGS |      1 |           27 |  2.485295e-01 |  5.000000e-01 |  3.202847e-02 |   1.229760e-02 |          2048 |
|  LBFGS |      1 |           28 |  2.482244e-01 |  1.000000e+00 |  4.270463e-02 |   8.970983e-03 |          2048 |
|  LBFGS |      1 |           29 |  2.479714e-01 |  1.000000e+00 |  3.558719e-03 |   7.393900e-03 |          2048 |
|  LBFGS |      1 |           30 |  2.477316e-01 |  1.000000e+00 |  3.202847e-02 |   3.268087e-03 |          2048 |
|  LBFGS |      1 |           31 |  2.476178e-01 |  2.500000e-01 |  3.202847e-02 |   5.445890e-03 |          2048 |
|  LBFGS |      1 |           32 |  2.474874e-01 |  1.000000e+00 |  1.779359e-02 |   3.535903e-03 |          2048 |
|  LBFGS |      1 |           33 |  2.473980e-01 |  1.000000e+00 |  7.117438e-03 |   2.821725e-03 |          2048 |
|  LBFGS |      1 |           34 |  2.472935e-01 |  1.000000e+00 |  3.558719e-03 |   2.699880e-03 |          2048 |
|  LBFGS |      1 |           35 |  2.471418e-01 |  1.000000e+00 |  3.558719e-03 |   1.242523e-02 |          2048 |
|  LBFGS |      1 |           36 |  2.469862e-01 |  1.000000e+00 |  2.846975e-02 |   7.895605e-03 |          2048 |
|  LBFGS |      1 |           37 |  2.469598e-01 |  1.000000e+00 |  2.135231e-02 |   6.657676e-03 |          2048 |
|  LBFGS |      1 |           38 |  2.466941e-01 |  1.000000e+00 |  3.558719e-02 |   4.654690e-03 |          2048 |
|  LBFGS |      1 |           39 |  2.466660e-01 |  5.000000e-01 |  1.423488e-02 |   2.885769e-03 |          2048 |
|  LBFGS |      1 |           40 |  2.465605e-01 |  1.000000e+00 |  3.558719e-03 |   4.562565e-03 |          2048 |
|=================================================================================================================|
| Solver |  Pass  |   Iteration  |   Objective   |     Step      |    Gradient   |    Relative    |  sum(beta~=0) |
|        |        |              |               |               |   magnitude   | change in Beta |               |
|=================================================================================================================|
|  LBFGS |      1 |           41 |  2.465362e-01 |  1.000000e+00 |  1.423488e-02 |   5.652180e-03 |          2048 |
|  LBFGS |      1 |           42 |  2.463528e-01 |  1.000000e+00 |  3.558719e-03 |   2.389759e-03 |          2048 |
|  LBFGS |      1 |           43 |  2.463207e-01 |  1.000000e+00 |  1.511170e-03 |   3.738286e-03 |          2048 |
|  LBFGS |      1 |           44 |  2.462585e-01 |  5.000000e-01 |  7.117438e-02 |   2.321693e-03 |          2048 |
|  LBFGS |      1 |           45 |  2.461742e-01 |  1.000000e+00 |  7.117438e-03 |   2.599725e-03 |          2048 |
|  LBFGS |      1 |           46 |  2.461434e-01 |  1.000000e+00 |  3.202847e-02 |   3.186923e-03 |          2048 |
|  LBFGS |      1 |           47 |  2.461115e-01 |  1.000000e+00 |  7.117438e-03 |   1.530711e-03 |          2048 |
|  LBFGS |      1 |           48 |  2.460814e-01 |  1.000000e+00 |  1.067616e-02 |   1.811714e-03 |          2048 |
|  LBFGS |      1 |           49 |  2.460533e-01 |  5.000000e-01 |  1.423488e-02 |   1.012252e-03 |          2048 |
|  LBFGS |      1 |           50 |  2.460111e-01 |  1.000000e+00 |  1.423488e-02 |   4.166762e-03 |          2048 |
|  LBFGS |      1 |           51 |  2.459414e-01 |  1.000000e+00 |  1.067616e-02 |   3.271946e-03 |          2048 |
|  LBFGS |      1 |           52 |  2.458809e-01 |  1.000000e+00 |  1.423488e-02 |   1.846440e-03 |          2048 |
|  LBFGS |      1 |           53 |  2.458479e-01 |  1.000000e+00 |  1.067616e-02 |   1.180871e-03 |          2048 |
|  LBFGS |      1 |           54 |  2.458146e-01 |  1.000000e+00 |  1.455008e-03 |   1.422954e-03 |          2048 |
|  LBFGS |      1 |           55 |  2.457878e-01 |  1.000000e+00 |  7.117438e-03 |   1.880892e-03 |          2048 |
|  LBFGS |      1 |           56 |  2.457519e-01 |  1.000000e+00 |  2.491103e-02 |   1.074764e-03 |          2048 |
|  LBFGS |      1 |           57 |  2.457420e-01 |  1.000000e+00 |  7.473310e-02 |   9.511878e-04 |          2048 |
|  LBFGS |      1 |           58 |  2.457212e-01 |  1.000000e+00 |  3.558719e-03 |   3.718564e-04 |          2048 |
|  LBFGS |      1 |           59 |  2.457089e-01 |  1.000000e+00 |  4.270463e-02 |   6.237270e-04 |          2048 |
|  LBFGS |      1 |           60 |  2.457047e-01 |  5.000000e-01 |  1.423488e-02 |   3.647573e-04 |          2048 |
|=================================================================================================================|
| Solver |  Pass  |   Iteration  |   Objective   |     Step      |    Gradient   |    Relative    |  sum(beta~=0) |
|        |        |              |               |               |   magnitude   | change in Beta |               |
|=================================================================================================================|
|  LBFGS |      1 |           61 |  2.456991e-01 |  1.000000e+00 |  1.423488e-02 |   5.666884e-04 |          2048 |
|  LBFGS |      1 |           62 |  2.456898e-01 |  1.000000e+00 |  1.779359e-02 |   4.697056e-04 |          2048 |
|  LBFGS |      1 |           63 |  2.456792e-01 |  1.000000e+00 |  1.779359e-02 |   5.984927e-04 |          2048 |
|  LBFGS |      1 |           64 |  2.456603e-01 |  1.000000e+00 |  1.403782e-03 |   5.414985e-04 |          2048 |
|  LBFGS |      1 |           65 |  2.456482e-01 |  1.000000e+00 |  3.558719e-03 |   6.506293e-04 |          2048 |
|  LBFGS |      1 |           66 |  2.456358e-01 |  1.000000e+00 |  1.476262e-03 |   1.284139e-03 |          2048 |
|  LBFGS |      1 |           67 |  2.456124e-01 |  1.000000e+00 |  3.558719e-03 |   8.636596e-04 |          2048 |
|  LBFGS |      1 |           68 |  2.455980e-01 |  1.000000e+00 |  1.067616e-02 |   9.861527e-04 |          2048 |
|  LBFGS |      1 |           69 |  2.455780e-01 |  1.000000e+00 |  1.067616e-02 |   5.102487e-04 |          2048 |
|  LBFGS |      1 |           70 |  2.455633e-01 |  1.000000e+00 |  3.558719e-03 |   1.228077e-03 |          2048 |
|  LBFGS |      1 |           71 |  2.455449e-01 |  1.000000e+00 |  1.423488e-02 |   7.864590e-04 |          2048 |
|  LBFGS |      1 |           72 |  2.455261e-01 |  1.000000e+00 |  3.558719e-02 |   1.090815e-03 |          2048 |
|  LBFGS |      1 |           73 |  2.455142e-01 |  1.000000e+00 |  1.067616e-02 |   1.701506e-03 |          2048 |
|  LBFGS |      1 |           74 |  2.455075e-01 |  1.000000e+00 |  1.779359e-02 |   1.504577e-03 |          2048 |
|  LBFGS |      1 |           75 |  2.455008e-01 |  1.000000e+00 |  3.914591e-02 |   1.144021e-03 |          2048 |
|  LBFGS |      1 |           76 |  2.454943e-01 |  1.000000e+00 |  2.491103e-02 |   3.015254e-04 |          2048 |
|  LBFGS |      1 |           77 |  2.454918e-01 |  5.000000e-01 |  3.202847e-02 |   9.837523e-04 |          2048 |
|  LBFGS |      1 |           78 |  2.454870e-01 |  1.000000e+00 |  1.779359e-02 |   4.328953e-04 |          2048 |
|  LBFGS |      1 |           79 |  2.454865e-01 |  5.000000e-01 |  3.558719e-03 |   7.126815e-04 |          2048 |
|  LBFGS |      1 |           80 |  2.454775e-01 |  1.000000e+00 |  5.693950e-02 |   8.992562e-04 |          2048 |
|=================================================================================================================|
| Solver |  Pass  |   Iteration  |   Objective   |     Step      |    Gradient   |    Relative    |  sum(beta~=0) |
|        |        |              |               |               |   magnitude   | change in Beta |               |
|=================================================================================================================|
|  LBFGS |      1 |           81 |  2.454686e-01 |  1.000000e+00 |  1.183730e-03 |   1.590246e-04 |          2048 |
|  LBFGS |      1 |           82 |  2.454612e-01 |  1.000000e+00 |  2.135231e-02 |   1.389570e-04 |          2048 |
|  LBFGS |      1 |           83 |  2.454506e-01 |  1.000000e+00 |  3.558719e-03 |   6.162089e-04 |          2048 |
|  LBFGS |      1 |           84 |  2.454436e-01 |  1.000000e+00 |  1.423488e-02 |   1.877414e-03 |          2048 |
|  LBFGS |      1 |           85 |  2.454378e-01 |  1.000000e+00 |  1.423488e-02 |   3.370852e-04 |          2048 |
|  LBFGS |      1 |           86 |  2.454249e-01 |  1.000000e+00 |  1.423488e-02 |   8.133615e-04 |          2048 |
|  LBFGS |      1 |           87 |  2.454101e-01 |  1.000000e+00 |  1.067616e-02 |   3.872088e-04 |          2048 |
|  LBFGS |      1 |           88 |  2.453963e-01 |  1.000000e+00 |  1.779359e-02 |   5.670260e-04 |          2048 |
|  LBFGS |      1 |           89 |  2.453866e-01 |  1.000000e+00 |  1.067616e-02 |   1.444984e-03 |          2048 |
|  LBFGS |      1 |           90 |  2.453821e-01 |  1.000000e+00 |  7.117438e-03 |   2.457270e-03 |          2048 |
|  LBFGS |      1 |           91 |  2.453790e-01 |  5.000000e-01 |  6.761566e-02 |   8.228766e-04 |          2048 |
|  LBFGS |      1 |           92 |  2.453603e-01 |  1.000000e+00 |  2.135231e-02 |   1.084233e-03 |          2048 |
|  LBFGS |      1 |           93 |  2.453540e-01 |  1.000000e+00 |  2.135231e-02 |   2.060005e-04 |          2048 |
|  LBFGS |      1 |           94 |  2.453482e-01 |  1.000000e+00 |  1.779359e-02 |   1.560883e-04 |          2048 |
|  LBFGS |      1 |           95 |  2.453461e-01 |  1.000000e+00 |  1.779359e-02 |   1.614693e-03 |          2048 |
|  LBFGS |      1 |           96 |  2.453371e-01 |  1.000000e+00 |  3.558719e-02 |   2.145835e-04 |          2048 |
|  LBFGS |      1 |           97 |  2.453305e-01 |  1.000000e+00 |  4.270463e-02 |   7.602088e-04 |          2048 |
|  LBFGS |      1 |           98 |  2.453283e-01 |  2.500000e-01 |  2.135231e-02 |   3.422253e-04 |          2048 |
|  LBFGS |      1 |           99 |  2.453246e-01 |  1.000000e+00 |  3.558719e-03 |   3.872561e-04 |          2048 |
|  LBFGS |      1 |          100 |  2.453214e-01 |  1.000000e+00 |  3.202847e-02 |   1.732237e-04 |          2048 |
|=================================================================================================================|
| Solver |  Pass  |   Iteration  |   Objective   |     Step      |    Gradient   |    Relative    |  sum(beta~=0) |
|        |        |              |               |               |   magnitude   | change in Beta |               |
|=================================================================================================================|
|  LBFGS |      1 |          101 |  2.453168e-01 |  1.000000e+00 |  1.067616e-02 |   3.065286e-04 |          2048 |
|  LBFGS |      1 |          102 |  2.453155e-01 |  5.000000e-01 |  4.626335e-02 |   3.402368e-04 |          2048 |
|  LBFGS |      1 |          103 |  2.453136e-01 |  1.000000e+00 |  1.779359e-02 |   2.215029e-04 |          2048 |
|  LBFGS |      1 |          104 |  2.453119e-01 |  1.000000e+00 |  3.202847e-02 |   4.142355e-04 |          2048 |
|  LBFGS |      1 |          105 |  2.453093e-01 |  1.000000e+00 |  1.423488e-02 |   2.186007e-04 |          2048 |
|  LBFGS |      1 |          106 |  2.453090e-01 |  1.000000e+00 |  2.846975e-02 |   1.338602e-03 |          2048 |
|  LBFGS |      1 |          107 |  2.453048e-01 |  1.000000e+00 |  1.423488e-02 |   3.208296e-04 |          2048 |
|  LBFGS |      1 |          108 |  2.453040e-01 |  1.000000e+00 |  3.558719e-02 |   1.294488e-03 |          2048 |
|  LBFGS |      1 |          109 |  2.452977e-01 |  1.000000e+00 |  1.423488e-02 |   8.328380e-04 |          2048 |
|  LBFGS |      1 |          110 |  2.452934e-01 |  1.000000e+00 |  2.135231e-02 |   5.149259e-04 |          2048 |
|  LBFGS |      1 |          111 |  2.452886e-01 |  1.000000e+00 |  1.779359e-02 |   3.650664e-04 |          2048 |
|  LBFGS |      1 |          112 |  2.452854e-01 |  1.000000e+00 |  1.067616e-02 |   2.633981e-04 |          2048 |
|  LBFGS |      1 |          113 |  2.452836e-01 |  1.000000e+00 |  1.067616e-02 |   1.804300e-04 |          2048 |
|  LBFGS |      1 |          114 |  2.452817e-01 |  1.000000e+00 |  7.117438e-03 |   4.251642e-04 |          2048 |
|  LBFGS |      1 |          115 |  2.452741e-01 |  1.000000e+00 |  1.779359e-02 |   9.018440e-04 |          2048 |
|  LBFGS |      1 |          116 |  2.452691e-01 |  1.000000e+00 |  2.135231e-02 |   9.941716e-05 |          2048 |
|=================================================================================================================|

Predict the test-set labels, construct a confusion matrix for the test set, and estimate the classification error for the test set.

UpdatedLabel = predict(UpdatedMdl,XTest);
UpdatedConfusionTest = confusionchart(YTest,UpdatedLabel);

Figure contains an object of type ConfusionMatrixChart.

UpdatedL = loss(UpdatedMdl,XTest,YTest)

UpdatedL = 
0.1284

The classification error decreases after resume updates the classification model with more iterations.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™. (since R2023a)

Usage notes and limitations:

The predict function supports code generation.

For more information, see Introduction to Code Generation.

Version History

Introduced in R2017b

expand all

R2023b: Kernel models support standardization of predictors

The fitckernel and fitrkernel functions support the standardization of numeric predictors. That is, in the call to either function, you can specify the Standardize value as true to center and scale each numeric predictor variable. Kernel models include Mu and Sigma properties that contain the means and standard deviations, respectively, used to standardize the predictors before training. The properties are empty when the fitting function does not perform any standardization.

R2023a: Generate C/C++ code for prediction

You can generate C/C++ code for the predict function.

R2022a: `Cost` property stores the user-specified cost matrix

Starting in R2022a, the Cost property stores the user-specified cost matrix, so that you can compute the observed misclassification cost using the specified cost value. The software stores normalized prior probabilities (Prior) that do not reflect the penalties described in the cost matrix. To compute the observed misclassification cost, specify the LossFun name-value argument as "classifcost" when you call the loss function.

Note that model training has not changed and, therefore, the decision boundaries between classes have not changed.

For training, the fitting function updates the specified prior probabilities by incorporating the penalties described in the specified cost matrix, and then normalizes the prior probabilities and observation weights. This behavior has not changed. In previous releases, the software stored the default cost matrix in the Cost property and stored the prior probabilities used for training in the Prior property. Starting in R2022a, the software stores the user-specified cost matrix without modification, and stores normalized prior probabilities that do not reflect the cost penalties. For more details, see Misclassification Cost Matrix, Prior Probabilities, and Observation Weights.

Some object functions use the Cost and Prior properties:

The loss function uses the cost matrix stored in the Cost property if you specify the LossFun name-value argument as "classifcost" or "mincost".
The loss and edge functions use the prior probabilities stored in the Prior property to normalize the observation weights of the input data.

If you specify a nondefault cost matrix when you train a classification model, the object functions return a different value compared to previous releases.

If you want the software to handle the cost matrix, prior probabilities, and observation weights in the same way as in previous releases, adjust the prior probabilities and observation weights for the nondefault cost matrix, as described in Adjust Prior Probabilities and Observation Weights for Misclassification Cost Matrix. Then, when you train a classification model, specify the adjusted prior probabilities and observation weights by using the Prior and Weights name-value arguments, respectively, and use the default cost matrix.

ClassificationKernel

Description

Creation

Properties

Kernel Classification Properties

Learner — Linear classification model type 'logistic' | 'svm'

NumExpansionDimensions — Number of dimensions of expanded space positive integer

KernelScale — Kernel scale parameter positive scalar

BoxConstraint — Box constraint positive scalar

Lambda — Regularization term strength nonnegative scalar

Mu — Predictor means numeric vector | []

Sigma — Predictor standard deviations numeric vector | []

FittedLoss — Loss function used to fit linear model 'hinge' | 'logit'

Regularization — Complexity penalty type 'ridge (L2)'

Other Classification Properties

CategoricalPredictors — Indices of categorical predictors vector of positive integers | []

ClassNames — Unique class labels categorical array | character array | logical vector | numeric vector | cell array of character vectors

Cost — Misclassification costs square numeric matrix

ModelParameters — Parameters used for training model structure

PredictorNames — Predictor names cell array of character vectors

ExpandedPredictorNames — Expanded predictor names cell array of character vectors

Prior — Prior class probabilities numeric vector

ResponseName — Response variable name character vector

ScoreTransform — Score transformation function to apply to predicted scores 'doublelogit' | 'invlogit' | 'ismax' | 'logit' | 'none' | function handle | ...

Object Functions

Examples

Train Kernel Classification Model

Predict Class Labels and Resume Training

Extended Capabilities

C/C++ Code Generation Generate C and C++ code using MATLAB® Coder™. (since R2023a)

Version History

R2023b: Kernel models support standardization of predictors

R2023a: Generate C/C++ code for prediction

R2022a: Cost property stores the user-specified cost matrix

See Also

`Learner` — Linear classification model type
`'logistic'` | `'svm'`

`NumExpansionDimensions` — Number of dimensions of expanded space
positive integer

`KernelScale` — Kernel scale parameter
positive scalar

`BoxConstraint` — Box constraint
positive scalar

`Lambda` — Regularization term strength
nonnegative scalar

`Mu` — Predictor means
numeric vector | `[]`

`Sigma` — Predictor standard deviations
numeric vector | `[]`

`FittedLoss` — Loss function used to fit linear model
`'hinge'` | `'logit'`

`Regularization` — Complexity penalty type
`'ridge (L2)'`

`CategoricalPredictors` — Indices of categorical predictors
vector of positive integers | `[]`

`ClassNames` — Unique class labels
categorical array | character array | logical vector | numeric vector | cell array of character vectors

`Cost` — Misclassification costs
square numeric matrix

`ModelParameters` — Parameters used for training model
structure

`PredictorNames` — Predictor names
cell array of character vectors

`ExpandedPredictorNames` — Expanded predictor names
cell array of character vectors

`Prior` — Prior class probabilities
numeric vector

`ResponseName` — Response variable name
character vector

`ScoreTransform` — Score transformation function to apply to predicted scores
`'doublelogit'` | `'invlogit'` | `'ismax'` | `'logit'` | `'none'` | function handle | ...

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™. (since R2023a)

R2022a: `Cost` property stores the user-specified cost matrix