featureSelectionClassificationKruskalWallisComponent

Pipeline component for performing feature selection using Kruskal-Wallis test

Since R2026a

Description

featureSelectionClassificationKruskalWallisComponent is a pipeline component that performs feature selection using p-values computed by the Kruskal-Wallis test. The pipeline component uses the functionality of the kruskalwallis function during the learn phase to identify important predictors in the data. During the run phase, the component selects the same predictors from a new data set.

Creation

Syntax

component = featureSelectionClassificationKruskalWallisComponent

component = featureSelectionClassificationKruskalWallisComponent(Name=Value)

Description

component = featureSelectionClassificationKruskalWallisComponent creates a pipeline component for feature selection using the Kruskal-Wallis test. Use the component when creating a pipeline for classification.

component = featureSelectionClassificationKruskalWallisComponent(Name=Value) sets writable Properties using one or more name-value arguments. For example, NumFeatures=10 specifies to select 10 important features.

Properties

Learn Parameters

The software sets learn parameters when you create the component. You can modify learn parameters using dot notation any time before you use the learn object function. Any unset learn parameters use the corresponding default values.

NumFeatures — Number of features to select

positive integer scalar

Number of features (predictors) to select, specified as a positive integer scalar.

If you do not specify the NumFeatures or RelativeScoreThreshold value, the software selects all features. You cannot specify both NumFeatures and RelativeScoreThresold.

Example: c = featureSelectionClassificationKruskalWallisComponent(NumFeatures=5)

Example: c.NumFeatures = 10

Data Types: single | double

RelativeScoreThreshold — Relative score threshold for selecting features

numeric scalar in the range (0,1]

Relative score threshold for selecting features, specified as a numeric scalar in the range (0,1].

• When the maximum feature (predictor) score is a finite value s_max, the software selects a feature with score s if s/s_max is greater than or equal to the RelativeScoreThreshold value.

• When the maximum feature score is infinite, the software selects each feature with an Inf score.

If you do not specify the NumFeatures or RelativeScoreThresold value, the software selects all features. You cannot specify both NumFeatures and RelativeScoreThresold.

Example: c = featureSelectionClassificationKruskalWallisComponent(RelativeScoreThreshold=0.5)

Example: c.RelativeScoreThreshold = 0.75

Data Types: single | double

Component Properties

The software sets component properties when you create the component. You can modify the component properties (excluding HasLearnables and HasLearned) using dot notation at any time. You cannot modify the HasLearnables and HasLearned properties directly.

Name — Component identifier

"FeatureSelectionClassificationKruskalWallis" (default) | character vector | string scalar

Component identifier, specified as a character vector or string scalar.

Example: c = featureSelectionClassificationKruskalWallisComponent(Name="FeatureSelector")

Example: c.Name = "KruskalWallisSelector"

Data Types: char | string

Inputs — Names of input ports

["X","Y"] (default) | character vector | string array | cell array of character vectors

Names of the input ports, specified as a character vector, string array, or cell array of character vectors.

Example: c = featureSelectionClassificationKruskalWallisComponent(Inputs=["Data1","Data2"])

Example: c.Inputs = ["X1","Y1"]

Data Types: char | string | cell

Outputs — Names of output ports

["XSelected","Scores"] (default) | character vector | string array | cell array of character vectors

Names of the output ports, specified as a character vector, string array, or cell array of character vectors.

Example: c = featureSelectionClassificationKruskalWallisComponent(Outputs=["newX","importance"])

Example: c.Outputs = ["X","S"]

Data Types: char | string | cell

InputTags — Tags that enable automatic connection of component inputs

[1 2] (default) | nonnegative integer vector

Tags that enable the automatic connection of the component inputs with other components or pipelines, specified as a nonnegative integer vector. If you specify InputTags, then the number of tags must match the number of inputs in Inputs.

Example: c = featureSelectionClassificationKruskalWallisComponent(InputTags=[1 0])

Example: c.InputTags = [1 2]

Data Types: single | double

OutputTags — Tags that enable automatic connection of component outputs

[1 NaN] (default) | nonnegative integer vector

Tags that enable the automatic connection of the component outputs with other components or pipelines, specified as a nonnegative integer vector. If you specify OutputTags, then the number of tags must match the number of outputs in Outputs.

Example: c = featureSelectionClassificationKruskalWallisComponent(OutputTags=[1 0])

Example: c.OutputTags=[1 2]

Data Types: single | double

HasLearnables — Indicator for learnables

Read-only: 1 (true) (default)

This property is read-only.

Indicator for the learnables, returned as 1 (true). A value of 1 indicates that the component contains Learnables.

Data Types: logical

HasLearned — Indicator showing learning status of component

Read-only: 0 (false) (default) | 1 (true)

This property is read-only.

Indicator showing the learning status of the component, returned as 0 (false) or 1 (true). A value of 1 indicates that the learn object function has been applied to the component and the Learnables are nonempty.

Data Types: logical

Learnables

The software sets learnables when you use the learn object function. You cannot modify learnables directly.

SelectedVariables — Names of features selected by component

Read-only: string array | []

This property is read-only.

Names of the features selected by the component, returned as a string array. The features correspond to columns in the first data argument of learn.

Data Types: string

UsedVariables — Names of variables used by component

Read-only: string array | []

This property is read-only.

Names of the variables used by the component to select features, returned as a string array. The variables correspond to columns in the first data argument of learn.

Data Types: string

Object Functions

learn	Initialize and evaluate pipeline or component
run	Execute pipeline or component for inference after learning
reset	Reset pipeline or component
series	Connect components in series to create pipeline
parallel	Connect components or pipelines in parallel to create pipeline
view	View diagram of pipeline inputs, outputs, components, and connections

Examples

Create a Pipeline Component for Kruskal-Wallis Feature Selection

Create a featureSelectionClassificationKruskalWallisComponent pipeline component. Specify to select 3 features

component = featureSelectionClassificationKruskalWallisComponent(NumFeatures=3)

component = 
  featureSelectionClassificationKruskalWallisComponent with properties:

                 Name: "FeatureSelectionClassificationKruskalWallis"
               Inputs: ["X"    "Y"]
            InputTags: [1 2]
              Outputs: ["XSelected"    "Scores"]
           OutputTags: [1 NaN]

   
Learnables (HasLearned = false)
    SelectedVariables: []
        UsedVariables: []

   
Learn Parameters (unlocked)
          NumFeatures: 3


Show all parameters

component is a featureSelectionClassificationKruskalWallisComponent object that contains two learnables: SelectedVariables and UsedVariables. These properties remains empty until you pass data to the component during the learn phase.

Read the fisheriris data set into a table. Store the predictor and response data in the tables X and Y, respectively.

fisheriris = readtable("fisheriris.csv");
X = fisheriris(:,1:end-1);
Y = fisheriris(:,end);

Use the learn object function to select features from the predictor data X.

component = learn(component,X,Y)

component = 
  featureSelectionClassificationKruskalWallisComponent with properties:

                 Name: "FeatureSelectionClassificationKruskalWallis"
               Inputs: ["X"    "Y"]
            InputTags: [1 2]
              Outputs: ["XSelected"    "Scores"]
           OutputTags: [1 NaN]

   
Learnables (HasLearned = true)
    SelectedVariables: ["PetalWidth"    "PetalLength"    "SepalLength"]
        UsedVariables: ["SepalLength"    "SepalWidth"    "PetalLength"    "PetalWidth"]

   
Learn Parameters (locked)
          NumFeatures: 3


Show all parameters

Note that the HasLearned property is set to true and the SelectedVariables and UsedVariables are nonempty.

Find the names of the selected features.

names = component.SelectedVariables

names = 

  1×3 string array

    "PetalWidth"    "PetalLength"    "SepalLength"

Version History

Introduced in R2026a