medianstats.java

peersim最新版1.0.4

/*
 * Copyright (c) 2003-2005 The BISON Project
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 */

package peersim.util;

import java.util.ArrayList;
import java.util.Collections;

/**
 * This class adds the ability to retrieve the median element to the
 * {@link IncrementalStats} class. Note that this class actually stores all
 * the elements, so (unlike in its superclass) storage requirements depend
 * on the number of items processed.
 * 
 * @author giampa
 */
public class MedianStats extends IncrementalStats
{

/** Structure to store each entry. */
private final ArrayList<Double> data=new ArrayList<Double>();

/** Calls {@link #reset}. */
public MedianStats()
{
	reset();
}

/**
 * Retrieves the median in the current data collection.
 * 
 * @return The current median value.
 */
public double getMedian()
{
	double result;

	if (data.isEmpty())
		throw new IllegalStateException("Data vector is empty!");

	// Sort the arraylist
	Collections.sort(data);
	if (data.size() % 2 != 0) { // odd number
		result = data.get(data.size() / 2);
	} else { // even number:
		double a = data.get(data.size() / 2);
		double b = data.get(data.size() / 2 - 1);
		result = (a + b) / 2;
	}
	return result;
}

public void add(double item, int k)
{
	for (int i = 0; i < k; ++i) {
		super.add(item, 1);
		data.add(new Double(item));
	}
}

public void reset()
{
	super.reset();
	if (data != null)
		data.clear();
}


public static void main( String[] args ) {
	MedianStats s = new MedianStats();
	for(int i=0; i<args.length; i++) s.add(Double.parseDouble(args[i]));
	System.out.println("Average: "+s.getAverage());
	System.out.println("Median: "+s.getMedian());
}

}