RunningExponentialAverage.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;

/**
 * Computes an exponential running average over a series of values.
 */
public class RunningExponentialAverage
{
	public double m_value = Double.NaN;

	/**
	 * Create an exponential average without an initial value
	 */
	public RunningExponentialAverage()
	{
		m_value = Double.NaN;
	}

	/**
	 * Create an exponential average with the given initial value
	 */
	public RunningExponentialAverage(final double initialValue)
	{
		m_value = initialValue;
	}

	/**
	 * Add the value to the average, weighting it with the giveen weight.
	 * 
	 * @param value
	 *            the value to add
	 * @param weight
	 *            the value's weight between 0 and 1.
	 */
	public void add(final double value, final double weight)
	{
		if(Double.isNaN(m_value))
		{
			m_value = value;
		}
		else
		{
			m_value = value * weight + m_value * (1.0 - weight);
		}
	}

	/**
	 * Return true until {@link #add(double, double)} has been called at least once for instances initialized without an initial value. Otherwise, always returns false.
	 */
	public boolean isEmpty()
	{
		return Double.isNaN(m_value);
	}

	/**
	 * Returns the current exponential average
	 * 
	 * @return exponential average
	 */
	public double get()
	{
		return m_value;
	}
}