Package ai.libs.jaicore.basic.metric

Class TransformDistance

java.lang.Object

ai.libs.jaicore.basic.metric.AWeightedTrigometricDistance

ai.libs.jaicore.basic.metric.TransformDistance

All Implemented Interfaces:

org.api4.java.common.math.IMetric<double[]>, IDistanceMetric

public class TransformDistance
extends AWeightedTrigometricDistance

Implementation of the Transform Distance (TD) measure as published in "Non-isometric transforms in time series classification using DTW" by Tomasz Gorecki and Maciej Luczak (2014). Building up on their work of the Derivate Distance, the authors were looking for functions other than the derivative which can be used in a similar manner, what leads them to use transform instead of derivates. Given a distance measure d, the Transform Distance for the two time series A and B is: a * d(A, B) + b * d(t(A), t(B)), where t(A) and t(B) are transforms (@see jaicore.ml.tsc.filter.transform) of A and B respec. and 0 <= a <= 1, 0 <= b <= 1> are parameters of the measure. The parameters a and b are set via an alpha value, that is a=cos(alpha) and b=sin(alpha). The Transform Distance that uses Dynamic Time Warping as underlying distance measure is commonly denoted as TD_DTW. The Transform Distance that uses the Euclidean distance as underlying distance measure is commonly denoted as TD_ED.

It is also possible to use a distinct distance measure to calculate the distance between the time series and its transforms.

Constructor Summary

Constructors

Constructor	Description
TransformDistance(double alpha, IVectorTransform transform, IDistanceMetric distance)	Constructor that uses the same distance measures for the function and transform values.
TransformDistance(double alpha, IVectorTransform transform, IDistanceMetric timeSeriesDistance, IDistanceMetric transformDistance)	Constructor with individual distance measures for the function and transform values.
TransformDistance(double alpha, IDistanceMetric distance)	Constructor that uses the same distance measures for the function and transform values that uses the CosineTransform as transformation.
TransformDistance(double alpha, IDistanceMetric timeSeriesDistance, IDistanceMetric transformDistance)	Constructor with individual distance measures for the function and transform values that uses the CosineTransform as transformation.

Method Summary

Modifier and Type	Method	Description
double	distance(double[] a, double[] b)	Calculates the distance between two time series.

Methods inherited from class ai.libs.jaicore.basic.metric.AWeightedTrigometricDistance

getA, getAlpha, getB, setAlpha

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.api4.java.common.metric.IDistanceMetric

getDistance

Constructor Detail

TransformDistance

public TransformDistance(double alpha,
                         IVectorTransform transform,
                         IDistanceMetric timeSeriesDistance,
                         IDistanceMetric transformDistance)

Constructor with individual distance measures for the function and transform values.

Parameters:

alpha -

transform - The transform calculation to use.

timeSeriesDistance - The distance measure to use to calculate the distance of the transform values.

transformDistance - The distance measure to use to calculate the distance of the transform values.

See Also:

,0 = alpha = pi/2.

TransformDistance

public TransformDistance(double alpha,
                         IDistanceMetric timeSeriesDistance,
                         IDistanceMetric transformDistance)

Constructor with individual distance measures for the function and transform values that uses the CosineTransform as transformation.

Parameters:

alpha - The distance measure to use to calculate the distance of the function values. 0 <= alpha <= pi/2.

timeSeriesDistance - The distance measure to use to calculate the distance of the transform values.

transformDistance - The distance measure to use to calculate the distance of the transform values.

TransformDistance

public TransformDistance(double alpha,
                         IVectorTransform transform,
                         IDistanceMetric distance)

Constructor that uses the same distance measures for the function and transform values.

Parameters:

alpha - The distance measure to use to calculate the distance of the function values. 0 <= alpha <= pi/2.

transform - The transform calculation to use.

distance - The distance measure to use to calculate the distance of the function and transform values.

TransformDistance

public TransformDistance(double alpha,
                         IDistanceMetric distance)

Constructor that uses the same distance measures for the function and transform values that uses the CosineTransform as transformation.

Parameters:

alpha - The distance measure to use to calculate the distance of the function values. 0 <= alpha <= pi/2.

distance - The distance measure to use to calculate the distance of the function and transform values.

Method Detail

distance

public double distance(double[] a,
                       double[] b)

Description copied from interface: IDistanceMetric

Calculates the distance between two time series.

Parameters:

a - The influence of distance of the function values to the overall distance measure.

b - The influence of distance of the transform values to the overall distance measure.

Returns:

Distance between the first and second time series.