org.jscience.computing.kmeans
Class Gaussian

java.lang.Object
  org.jscience.computing.kmeans.Gaussian

public class Gaussian
extends java.lang.Object

This class implements the Gaussian activation function.

Field Summary

static float	DEF_MU Default value of mu.
static float	DEF_SIGMA Default value of sigma.
static float	MIN_SIGMA Minimum value for sigma.

Constructor Summary

Gaussian()
Default constructor.

Method Summary

float	getMu() Accessor for Gaussian mu (mean) parameter.
float	getOutput(float x) Calculate the value of a Gaussian function for a given input.
float	getOutputPrime(float x) Calculate the value of the derivative of a Gaussian function for a given input.
float	getSigma() Accessor for Gaussian sigma (std. dev.) parameter.
void	initDefaults() Initialize the function parameters to their default values.
static void	main(java.lang.String[] args) DOCUMENT ME!
void	setMu(float m) Mutator for Gaussian mu parameter.
void	setSigma(float s) Mutator for Gaussian sigma parameter.

Methods inherited from class java.lang.Object

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

Field Detail

DEF_MU

public static final float DEF_MU

Default value of mu.

See Also:

Constant Field Values

MIN_SIGMA

public static final float MIN_SIGMA

Minimum value for sigma.

See Also:

Constant Field Values

DEF_SIGMA

public static final float DEF_SIGMA

Default value of sigma.

See Also:

Constant Field Values

Constructor Detail

Gaussian

public Gaussian()

Default constructor.

Method Detail

getMu

public float getMu()

Accessor for Gaussian mu (mean) parameter.

Returns:

float - the value of mu.

setMu

public void setMu(float m)

Mutator for Gaussian mu parameter.

Parameters:

m - m - the new value for mu.

getSigma

public float getSigma()

Accessor for Gaussian sigma (std. dev.) parameter.

Returns:

float - the value of sigma.

setSigma

public void setSigma(float s)

Mutator for Gaussian sigma parameter.

Parameters:

s - s - the new value for sigma.

initDefaults

public void initDefaults()

Initialize the function parameters to their default values.

getOutput

public float getOutput(float x)

Calculate the value of a Gaussian function for a given input. The Gaussian or normal probability function is given by:

 1                -(x-mu)^2 / (2 * sigma^2)
 y  =  ------------------- *  e
 (2 * pi * sigma)^0.5
 

 

The variable k1 holds the value of the first term, and k2 holds the value of the 1 / (2 simga^2) term for the current value of sigma.

Parameters:

x - - the input value.

Returns:

float - the corresponding value of y.

getOutputPrime

public float getOutputPrime(float x)

Calculate the value of the derivative of a Gaussian function for a given input. The derivative of the Gaussian function is given by:

 

 y'(x)  =  y(x) * -2k2(x - mu)
 

 

 

The variable k1 holds the value of the first term, and k2 holds the value of the 1 / (2 simga^2) term for the current value of sigma.

Parameters:

x - - the input value.

Returns:

float - the corresponding value of y prime.

main

public static void main(java.lang.String[] args)

DOCUMENT ME!

Parameters:

args - DOCUMENT ME!