step.java

利用Java实现的神经网络工具箱

/*
 * $RCSfile: Step.java,v $
 * $Revision: 1.2 $
 * $Date: 2004/10/17 02:47:42 $
 *
 * NeuralNetworkToolkit
 * Copyright (C) 2004 Universidade de Brasília
 *
 * This file is part of NeuralNetworkToolkit.
 *
 * NeuralNetworkToolkit is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * NeuralNetworkToolkit is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with NeuralNetworkToolkit; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA - 02111-1307 - USA.
 */

package neuralnetworktoolkit.activationfunctions;

/**
 * Step activation function.
 * 
 * @version $Revision: 1.2 $ - $Date: 2004/10/17 02:47:42 $
 * 
 * @author <a href="mailto:[e-mail]">Hugo Iver V. Gonçalves</a>
 * @author <a href="mailto:[e-mail]">Rodrigo C. M. Coimbra</a>
 */
public class Step extends ActivationFunction {
	/** Default height value. */
	public static final double DEFAULT_HEIGHT = 1;
	/** Default horizontal displacement value. */
	public static final double DEFAULT_HORIZONTAL_DISPLACEMENT = 0;
	/** Default vertical displacement value. */
	public static final double DEFAULT_VERTICAL_DISPLACEMENT = 0;
	/** Step height. */
	private double height;
	/** Step horizontal displacement. */
	private double horizontalDisplacement;
	/** Step vertical displacement. */
	private double verticalDisplacement;
	/** Auto-reference to provide the unique class instance. */
	private static Step function;

	/**
	 * Creates a new Step activation function.
	 */
	public Step() {
		functionName = "Step";
		functionExpression = "if (x >= horizontalDisplacement)/n"
							+ "value = height + verticalDisplacement;/n"
							+ "else value = verticalDisplacement";
		functionDerivativeExpression = "1";
		height = DEFAULT_HEIGHT;
		horizontalDisplacement = DEFAULT_HORIZONTAL_DISPLACEMENT;
		verticalDisplacement = DEFAULT_VERTICAL_DISPLACEMENT;
		
	} //Step()
	
	/**
	 * Returns the unique instance of <code>Step</code>.
	 * 
	 * @return Unique instance of <code>Step</code>.
	 */
	public static Step instantiate() {
		if(function == null) {
			function = new Step();
			
		}
		
		return function;
		
	} //instantiate()

	/* 
	 * @see neuralnetworktoolkit.activationfunctions.IActivationFunction#functionValue(double)
	 */
	public double functionValue(double input) {
		double value;
		
		if (input >= horizontalDisplacement) {
			value = height + verticalDisplacement;
			
		} else {
			value = verticalDisplacement;
			
		}
		
		return value;
				
	} //functionValue()

	/* 
	 * @see neuralnetworktoolkit.activationfunctions.IActivationFunction#functionDerivative(double)
	 */
	public double functionDerivative(double input) {
		return 1;
		
	} //functionDerivative()

	/**
	 * Returns the step height value.
	 * 
	 * @return Returns the height.
	 */
	public double getHeight() {
		return height;
		
	} //getHeight()
	
	/**
	 * Sets the step height value.
	 * 
	 * @param height The height to set.
	 */
	public void setHeight(double height) {
		this.height = height;
		
	} //setHeight()
	
	/**
	 * Returns the step horizontal displacement value.
	 * 
	 * @return Returns the horizontal displacement.
	 */
	public double getHorizontalDisplacement() {
		return horizontalDisplacement;
		
	} //getHorizontalDisplacement()
	
	/**
	 * Sets the step horizontal displacement value.
	 * 
	 * @param horizontalDisplacement The horizontal displacement to set.
	 */
	public void setHorizontalDisplacement(double horizontalDisplacement) {
		this.horizontalDisplacement = horizontalDisplacement;
		
	} //setHorizontalDisplacement()
	
	/**
	 * Returns the step vertical displacement value.
	 * 
	 * @return Returns the vertical displacement.
	 */
	public double getVerticalDisplacement() {
		return verticalDisplacement;
		
	} //getVerticalDisplacement()
	
	/**
	 * Sets the step vertical displacement value.
	 * 
	 * @param verticalDisplacement The vertical displacement to set.
	 */
	public void setVerticalDisplacement(double verticalDisplacement) {
		this.verticalDisplacement = verticalDisplacement;
		
	} //setVerticalDisplacement()
	
} //Step