package org.djutils.means;
   
   /**
    * Compute the geometric (weighted) mean of a set of values. Geometric mean can not handle negative or zero values.
    * <p>
    * Copyright (c) 2013-2016 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
    * BSD-style license. See <a href="https://djutils.org/docs/current/djutils/licenses.html">DJUTILS License</a>.
    * </p>
    * @author <a href="https://www.tudelft.nl/averbraeck">Alexander Verbraeck</a>
   * @author <a href="https://www.tudelft.nl/staff/p.knoppers/">Peter Knoppers</a>
   * @param <V> value type
   * @param <W> weight type
   */
  public class GeometricMean<V extends Number, W extends Number> extends AbstractMean<GeometricMean<V, W>, V, W>
  {
  
      @Override
      public final double getMean()
      {
          return Math.exp(getSum() / getSumOfWeights());
      }
  
      @Override
      public final GeometricMean<V, W> addImpl(final V value, final Number weight)
      {
          increment(Math.log(value.doubleValue()) * weight.doubleValue(), weight.doubleValue());
          return this;
      }
  
      @Override
      public final String toString()
      {
          return "GeometricMean [current sum of logarithmic values=" + getSum() + ", current sum of weights=" + getSumOfWeights()
                  + ", current geometric mean=" + getMean() + "]";
      }
  
  }