Package org.apache.commons.math4.neuralnet.sofm

Class NeighbourhoodSizeFunctionFactory

java.lang.Object

org.apache.commons.math4.neuralnet.sofm.NeighbourhoodSizeFunctionFactory

public final class NeighbourhoodSizeFunctionFactory
extends Object

Factory for creating instances of NeighbourhoodSizeFunction.

Since:

3.3

Method Summary

Modifier and Type	Method	Description
static NeighbourhoodSizeFunction	exponentialDecay(double initValue, double valueAtNumCall, long numCall)	Creates an exponential decay function.
static NeighbourhoodSizeFunction	quasiSigmoidDecay(double initValue, double slope, long numCall)	Creates an sigmoid-like NeighbourhoodSizeFunction function.

Methods inherited from class java.lang.Object

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

Method Detail

exponentialDecay

public static NeighbourhoodSizeFunction exponentialDecay(double initValue,
                                                         double valueAtNumCall,
                                                         long numCall)

Creates an exponential decay function. It will compute a e-x / b, where x is the (integer) independent variable and

• a = initValue
• b = -numCall / ln(valueAtNumCall / initValue)

Parameters:

initValue - Initial value, i.e. value(0).

valueAtNumCall - Value of the function at numCall.

numCall - Argument for which the function returns valueAtNumCall.

Returns:

the neighbourhood size function.

Throws:

IllegalArgumentException - if initValue <= 0, valueAtNumCall <= 0, valueAtNumCall >= initValue or numCall <= 0.

quasiSigmoidDecay

public static NeighbourhoodSizeFunction quasiSigmoidDecay(double initValue,
                                                          double slope,
                                                          long numCall)

Creates an sigmoid-like NeighbourhoodSizeFunction function. The function f will have the following properties:

• f(0) = initValue
• numCall is the inflexion point
• slope = f'(numCall)

Parameters:

initValue - Initial value, i.e. value(0).

slope - Value of the function derivative at numCall.

numCall - Inflexion point.

Returns:

the neighbourhood size function.

Throws:

IllegalArgumentException - if initValue <= 0, slope >= 0 or numCall <= 0.