kohonenneuron.java

Kohonen network nural, framework for java developer

/**
* Copyright (c) 2006, Seweryn Habdank-Wojewodzki
* Copyright (c) 2006, Janusz Rybarski
*
* All rights reserved.
* 
* Redistribution and use in source and binary forms,
* with or without modification, are permitted provided
* that the following conditions are met:
*
* Redistributions of source code must retain the above
* copyright notice, this list of conditions and the
* following disclaimer.
*
* Redistributions in binary form must reproduce the
* above copyright notice, this list of conditions
* and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS
* AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
* THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
* WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*/

package network;

import activationFunction.ActivationFunctionModel;
import java.util.Random;
import metrics.MetricModel;
import activationFunction.*;
import metrics.*;

/**
 * Class representing <B>neuron</B> with bias and specyfied 
 * activation function
 * 
 * @author Janusz Rybarski
 * e-mail: janusz.rybarski AT ae DOT krakow DOT pl
 * @author Seweryn Habdank-Wojewdzki
 * e-mail: habdank AT megapolis DOT pl
 * @version 1.0 2006/07/09
 * @see ActivationFunctionModel
 */

public class KohonenNeuron implements NeuronModel{
    
    /**
     * array of the weight
     */
    private double[] weight;
    /**
     * activation function
     */
    private ActivationFunctionModel activationFunction;
    
    /**
     * calculates distance beetwen input vector and neurons weigths
    */
    
    private MetricModel distanceFunction;
    
    /**
     * Creates new neuron with specyfied numbers of weight. 
     * Value of the weight is random where max value is definited by maxWeight.
     * Activation function is definied by activationFunction parameter.
     * @param weightNumber numbers of weight
     * @param maxWeight max value of the weight
     * @param activationFunction activation function
     */
    public KohonenNeuron(int weightNumber, double[] maxWeight, ActivationFunctionModel activationFunction){
        if(weightNumber == maxWeight.length){
            Random rand = new Random();
            weight = new double[weightNumber];
            for(int i=0; i< weightNumber; i++){
                weight[i] = rand.nextDouble() * maxWeight[i];
            }
        }
        this.activationFunction = activationFunction;
    }
    
    /**
     * Creates new neuron with weight specyfied by array and specified activation funciton. 
     * Numbers of weights are the same as length of the array.
     * @param weightArray array of the weight
     * @param activationFunction activation function
     */
    public KohonenNeuron(double[] weightArray,ActivationFunctionModel activationFunction) {
        int weightSize = weightArray.length;
        weight = new double[weightSize];
        for(int i=0; i< weightSize; i++){
            weight[i] = weightArray[i];
        }
        this.activationFunction = activationFunction;
    }
    
    /**
     * Return array of neuron weigths
     * @return array of neuron weigths
     */
    public double[] getWeight(){
        return weight.clone();
    }
    
    /**
     * Return value of the neuron after activation.
     * if activation function is not set, function 
     * return sum of the multiplication of vector v_i
     * and weight w_i for each i (numbers of weigth and
     * lenght of the input vector)
     * @param inputVector input vector for neuron
     * @return return
     */
    public double getValue(double[] inputVector){
        double value = 0;
        int inputSize = inputVector.length;
        if ( distanceFunction != null){
            value = distanceFunction.getDistance(weight, inputVector);
        }else{
            for(int i=0; i< inputSize; i++){
                value = value + inputVector[i] * weight[i];
            }
        }
        if( activationFunction != null)
            return activationFunction.getValue(value);
        else
            return value;
    }
    
    /**
     * Set weigths from array as parameter
     * @param weight array of the weights
     */
    public void setWeight(double[] weight){
        for (int i=0; i< weight.length; i++){
            this.weight[i] = weight[i];
        }
    }
    
    /**
     * Returns a string representation of the NeuronModel.
     * NeuronModel is describe by its weights [w_1,w_2,...]
     * 
     * @return a string representation of the NeuronModel
     */
    public String toString(){
        String text="";
        text += "[ ";
        int weightSize = weight.length;
        for (int i=0; i< weightSize; i++){
            text += weight[i];
            if(i < weightSize -1 ){
                text += ", ";
            }
        }
        text += " ]";
        return text;
    }

    /**
     * Return reference to distance function
     * @return reference to distance function
     */
    public MetricModel getDistanceFunction() {
        return distanceFunction;
    }

    /**
     * Set distance function
     * @param distanceFunction reference to distance function
     */
    public void setDistanceFunction(MetricModel distanceFunction) {
        this.distanceFunction = distanceFunction;
    }
}