simplepeakfinder.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.tools.math;

import java.util.List;
import java.util.LinkedList;

public class SimplePeakFinder implements PeakFinder {

    private int numberOfNeighbours = 5;

    public SimplePeakFinder(int neighbours) {
	this.numberOfNeighbours = neighbours;
    }

    /** Returns a list with peaks. */
    public List getPeaks(Peak[] series) {
	List result = new LinkedList();
	for (int i = 0; i < series.length; i++) {
	    if (isPeak(series, i)) {
		result.add(series[i]);
	    }
	}
	return result;
    }

    /** Returns true if the value for index is an extremum of the given type between the given numbers 
     *  of neighbours. */
    private boolean isPeak(Peak[] series, int index) {
	boolean ok = false;
	int current = index;
	int okValues = 0;

	// values to left
	while (!ok) {
	    current--;
	    if (current < 0)
		return false;
	    if (!isOk(series, current, index))
		return false;
	    okValues++;
	    if (okValues > numberOfNeighbours)
		ok = true;
	}
	ok = false;
	current = index;
	okValues = 0;
	// values to right
	while (!ok) {
	    current++;
	    if (current >= series.length)
		return false;
	    if (!isOk(series, current, index))
		return false;
	    okValues++;
	    if (okValues > numberOfNeighbours)
		ok = true;
	}
	return true;
    }
    

    /** In the minimum case this method returns true, if the current value is bigger than the index value. */
    private boolean isOk(Peak[] series, int current, int index) {
	if (series[current].getMagnitude() <= series[index].getMagnitude())
	    return false;
	else
	    return true;
    }
}