performancecriterion.java

一个很好的LIBSVM的JAVA源码。对于要研究和改进SVM算法的学者。可以参考。来自数据挖掘工具YALE工具包。

/*
 *  YALE - Yet Another Learning Environment
 *  Copyright (C) 2001-2004
 *      Simon Fischer, Ralf Klinkenberg, Ingo Mierswa, 
 *          Katharina Morik, Oliver Ritthoff
 *      Artificial Intelligence Unit
 *      Computer Science Department
 *      University of Dortmund
 *      44221 Dortmund,  Germany
 *  email: [e-mail]
 *  web:   http://yale.cs.uni-dortmund.de/
 *
 *  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., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 *  USA.
 */
package edu.udo.cs.yale.operator.performance;

import edu.udo.cs.yale.tools.math.Averagable;
import edu.udo.cs.yale.example.ExampleSet;
import edu.udo.cs.yale.example.Example;
import edu.udo.cs.yale.tools.LogService;
import edu.udo.cs.yale.operator.ResultObjectAdapter;

import java.util.*;
import java.text.*;

/** Each <tt>PerformanceCriterion</tt> contains a method to compute this
 *  criterion on a given set of examples, each which has to have a real and a
 *  predicted label.
 *  <br>
 *  PerformanceCriteria must implement the <tt>compareTo</tt> method in a way that
 *  allows <tt>Collections</tt> to sort the criteria in ascending order and 
 *  determine the best as the maximum.
 *
 *  @author Ingo
 *  @version $Id: PerformanceCriterion.java,v 2.15 2004/08/27 11:57:43 ingomierswa Exp $
 */
public abstract class PerformanceCriterion extends Averagable {

    /** Returns the fitness depending on the value. */
    public abstract double getFitness();

    /** Returns the maximum fitness. The default implementation resturns POSITIVE_INFINITY, subclasses may override
     *  this to allow feature operators to end the optimization if the maximum was reached. */
    public double getMaxFitness() { return Double.POSITIVE_INFINITY; }

    /**
     * The semantics of this method follow the specification in the interface
     * <tt>java.lang.Comparable</tt> in the following way: Two objects of this
     * class are equal if their <b>getFitness()</b> values are equal. The return
     * value is 0 in this case. If the specified object is not an object of this
     * class, a ClassCastException is thrown. If the given object has fitness bigger than this
     * object, the return value is -1. If the given object has fitness smaller than
     * this object, 1 is returned. No attributes other than error are used to
     * compare two objects of this class!
     *
     * @param o Object of this class to compare this object to.
     * @return -1, 0 or 1 if the specified object is greater than, equal to, or
     *          less than this object.
     */
    public int compareTo(Object o) {
	if (!this.getClass().equals(o.getClass())) 
	    throw new RuntimeException("Mismatched criterion class:"+this.getClass()+", "+o.getClass());
	PerformanceCriterion pc = (PerformanceCriterion)o;
	if (!pc.getName().equals(this.getName()))
	    throw new RuntimeException("Mismatched criterion type:"+this.getName()+", "+pc.getName());
	return Double.compare(this.getFitness(), pc.getFitness());
    }
}