Class FeatureUnion<T>

Namespace

AiDotNet.Preprocessing

Assembly

AiDotNet.dll

Concatenates results from multiple transformers horizontally.

public class FeatureUnion<T> : TransformerBase<T, Matrix<T>, Matrix<T>>, IDataTransformer<T, Matrix<T>, Matrix<T>>

Type Parameters

T

The numeric type for calculations (e.g., float, double).

Inheritance

object

TransformerBase<T, Matrix<T>, Matrix<T>>

FeatureUnion<T>

Implements

IDataTransformer<T, Matrix<T>, Matrix<T>>

Inherited Members

TransformerBase<T, Matrix<T>, Matrix<T>>.NumOps

TransformerBase<T, Matrix<T>, Matrix<T>>.Engine

TransformerBase<T, Matrix<T>, Matrix<T>>.IsFitted

TransformerBase<T, Matrix<T>, Matrix<T>>.ColumnIndices

TransformerBase<T, Matrix<T>, Matrix<T>>.SupportsInverseTransform

TransformerBase<T, Matrix<T>, Matrix<T>>.Fit(Matrix<T>)

TransformerBase<T, Matrix<T>, Matrix<T>>.Transform(Matrix<T>)

TransformerBase<T, Matrix<T>, Matrix<T>>.FitTransform(Matrix<T>)

TransformerBase<T, Matrix<T>, Matrix<T>>.InverseTransform(Matrix<T>)

TransformerBase<T, Matrix<T>, Matrix<T>>.GetFeatureNamesOut(string[])

TransformerBase<T, Matrix<T>, Matrix<T>>.FitCore(Matrix<T>)

TransformerBase<T, Matrix<T>, Matrix<T>>.TransformCore(Matrix<T>)

TransformerBase<T, Matrix<T>, Matrix<T>>.InverseTransformCore(Matrix<T>)

TransformerBase<T, Matrix<T>, Matrix<T>>.ValidateInputData(Matrix<T>)

TransformerBase<T, Matrix<T>, Matrix<T>>.EnsureFitted()

TransformerBase<T, Matrix<T>, Matrix<T>>.GetColumnsToProcess(int)

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Remarks

FeatureUnion applies multiple transformers to the same input data and concatenates their outputs into a single feature matrix. This is useful for combining different feature extraction methods.

Each transformer receives the full input matrix and produces its own output. All outputs are then concatenated column-wise.

For Beginners: Sometimes you want multiple feature sets from the same data: - Polynomial features from numeric columns - Statistics (mean, std) from time windows - Both PCA and manual feature engineering

FeatureUnion runs all transformers and combines their outputs side by side.

Constructors

FeatureUnion()

Creates a new instance of FeatureUnion<T>.

public FeatureUnion()

Properties

SupportsInverseTransform

Gets whether this transformer supports inverse transformation.

public override bool SupportsInverseTransform { get; }

Property Value

bool

Methods

Add(IDataTransformer<T, Matrix<T>, Matrix<T>>)

Adds a transformer to the union.

public FeatureUnion<T> Add(IDataTransformer<T, Matrix<T>, Matrix<T>> transformer)

Parameters

transformer IDataTransformer<T, Matrix<T>, Matrix<T>>

The transformer to add.

Returns

FeatureUnion<T>

This instance for method chaining.

Add(string, IDataTransformer<T, Matrix<T>, Matrix<T>>)

Adds a transformer to the union.

public FeatureUnion<T> Add(string name, IDataTransformer<T, Matrix<T>, Matrix<T>> transformer)

Parameters

name string

Name identifier for the transformer.

transformer IDataTransformer<T, Matrix<T>, Matrix<T>>

The transformer to add.

Returns

FeatureUnion<T>

This instance for method chaining.

FitCore(Matrix<T>)

Fits all transformers to the input data.

protected override void FitCore(Matrix<T> data)

Parameters

data Matrix<T>

The training data matrix.

GetFeatureNamesOut(string[]?)

Gets the output feature names after transformation.

public override string[] GetFeatureNamesOut(string[]? inputFeatureNames = null)

Parameters

inputFeatureNames string[]

Returns

string[]

GetTransformer(string)

Gets the transformer with the specified name.

public IDataTransformer<T, Matrix<T>, Matrix<T>>? GetTransformer(string name)

Parameters

name string

The transformer name.

Returns

IDataTransformer<T, Matrix<T>, Matrix<T>>

The transformer if found, null otherwise.

GetTransformerNames()

Gets all transformer names.

public string[] GetTransformerNames()

Returns

string[]

Array of transformer names.

GetTransformerOutputWidths()

Gets the number of output features from each transformer.

public Dictionary<string, int> GetTransformerOutputWidths()

Returns

Dictionary<string, int>

Dictionary mapping transformer name to output width.

InverseTransformCore(Matrix<T>)

Inverse transformation is not supported for FeatureUnion.

protected override Matrix<T> InverseTransformCore(Matrix<T> data)

Parameters

data Matrix<T>

Returns

Matrix<T>

TransformCore(Matrix<T>)

Transforms the data by applying all transformers and concatenating outputs.

protected override Matrix<T> TransformCore(Matrix<T> data)

Parameters

data Matrix<T>

The data to transform.

Returns

Matrix<T>

The concatenated transformed features.