RunningWeightedAverage.java

/*
 * This file is part of AirReceiver.
 *
 * AirReceiver 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 3 of the License, or
 * (at your option) any later version.

 * AirReceiver 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 AirReceiver.  If not, see <http://www.gnu.org/licenses/>.
 */

package org.dyndns.jkiddo.raop.server.airreceiver;

public class RunningWeightedAverage
{
	public final int m_length;
	public final double[] m_values;
	public final double[] m_weights;
	public boolean m_empty = true;
	public int m_index;
	public double m_average = Double.NaN;

	RunningWeightedAverage(final int windowLength)
	{
		m_length = windowLength;
		m_values = new double[m_length];
		m_weights = new double[m_length];
	}

	public boolean isEmpty()
	{
		return m_empty;
	}

	public void add(final double value, final double weight)
	{
		m_values[m_index] = value;
		m_weights[m_index] = weight;
		m_index = (m_index + 1) % m_length;
		m_average = Double.NaN;
		m_empty = false;
	}

	public double get()
	{
		if(!m_empty && Double.isNaN(m_average))
		{
			double vsum = 0;
			double wsum = 0;
			for(int i = 0; i < m_length; ++i)
			{
				vsum += m_values[i] * m_weights[i];
				wsum += m_weights[i];
			}
			if(wsum != 0.0)
				m_average = vsum / wsum;
		}

		return m_average;
	}
}