fouriergenerator.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.features;

import edu.udo.cs.yale.example.Attribute;
import edu.udo.cs.yale.example.AttributeWeightedExampleSet;
import edu.udo.cs.yale.example.ExampleSet;
import edu.udo.cs.yale.example.Example;
import edu.udo.cs.yale.example.ExampleReader;
import edu.udo.cs.yale.tools.RandomGenerator;
import edu.udo.cs.yale.generator.*;

import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.LinkedList;

/** This PopulationOperator generates new attributes in an individual's example table. 
 *  Each piecewise continous function can be synthesized with help of a Fourier synthesis, i.e.
 *  with a sum of trigonometric function with different frequencies and phases. This pop op 
 *  searches for the best frequencies and construct the corresponding trigonometric functions
 *  as new attributes.
 *  
 *  For each attribute <code>a</code> of the individuals the following is done:
 *  <ol>
 *    <li>The label is seen as function of the attribute <code>a</code></li>
 *    <li>A fast fourier transform is performed to search the <code>k</code> biggest 
 *        frequencies <code>f_k</code>in this attributes space (and their phase 
 *        differences <code>p_k</code>).</li>
 *    <li>For each of these <code>k</code> frequencies a new attribute is generated: 
 *        <code>sin(f_k * a) + p_k</code>.</li>
 *  </ol>
 *
 *  @author ingo
 *  @version $Id: FourierGenerator.java,v 1.8 2004/08/27 11:57:36 ingomierswa Exp $
 */
public class FourierGenerator extends IndividualOperator {

    /** The sinus factory. */
    private SinusFactory factory = null;

    private int startGenerations = 0;
    private int applyInGeneration = 1;

    /** Creates a new fourier generator. */
    public FourierGenerator(int maxPeaks, int adaptionType, int attributesPerPeak, double epsilon) {
	this.factory = new SinusFactory(maxPeaks);
	factory.setAdaptionType(adaptionType);
	factory.setEpsilon(epsilon);
	factory.setAttributePerPeak(attributesPerPeak);
    }

    public void setStartGenerations(int startGenerations) {
	this.startGenerations = startGenerations;
    }

    public void setApplyInGeneration(int applyInGeneration) {
	this.applyInGeneration = applyInGeneration;
    }

    public boolean performOperation(int generation) { 
	return 
	    (generation <= startGenerations) || 
	    ((applyInGeneration != 0) && ((generation % applyInGeneration) == 0));
    }

    public List operate(AttributeWeightedExampleSet exampleSet) throws Exception {
	Attribute label = exampleSet.getLabel();
	List attributes = new LinkedList();
	double totalMaxEvidence = Double.NEGATIVE_INFINITY;
	
	for (int i = 0; i < exampleSet.getNumberOfAttributes(); i++) {
	    Attribute current = exampleSet.getAttribute(i);
            // must be numeric and not contain sin!
	    if ((!current.isNominal()) && (current.getConstructionDescription().indexOf("sin") == -1)) { 
		List peaks = factory.getAttributePeaks(exampleSet, label, current);
		attributes.addAll(peaks);
	    }
	}

	if (attributes.size() > 0)
	    factory.generateSinusFunctions(exampleSet, attributes);

	// return example set as result
 	List result = new LinkedList();
 	result.add(exampleSet);
 	return result;
    }
}