gauss.java

来自「一个数据挖掘软件ALPHAMINERR的整个过程的JAVA版源代码」· Java 代码 · 共 89 行

/*
 *    This program 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.
 *
 *    This program 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 this program; if not, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/**
 * Title: XELOPES Data Mining Library
 * Description: The XELOPES library is an open platform-independent and data-source-independent library for Embedded Data Mining.
 * Copyright: Copyright (c) 2002 Prudential Systems Software GmbH
 * Company: ZSoft (www.zsoft.ru), Prudsys (www.prudsys.com)
 * @author Michael Thess
 * @author Valentine Stepanenko ([e-mail])
 * @version 1.2
 */

package com.prudsys.pdm.Models.Regression.NeuralNetwork.ActivationFunctions;

import com.prudsys.pdm.Models.Regression.NeuralNetwork.*;

/**
  * Gaussian activation function.
  */
public class Gauss extends ActivationFunction
{

   // -----------------------------------------------------------------------
   //  Methods of function calculation
   // -----------------------------------------------------------------------
   /**
    * Returns type of activation function as string.
    *
    * @return type of activation function
    */
   public String getFunctionType() {

     return ActivationFunction.GAUSS;
   }

   /**
    * Calculates the function value.
    *
    * @param value argument
    * @return function value, NaN if not defined
    */
   public double function(double value) {

     return Math.exp( -value*value );
   }

   /**
    * Calculates the reverse function value.
    *
    * @param value argument
    * @return reverse function value, NaN if not defined
    */
   public double reverseFunction(double value) {

     value = Math.log(value);
     if ( Double.isNaN(value) ) return value;

     return Math.sqrt(-value);
   }

   /**
    * First derivation of function.
    *
    * @param value argument
    * @return first deruvation, NaN if not defined
    */
   public double derivation(double value) {

     double f = function(value);

     return -2*value*f;
   }

}