package org.opentrafficsim.kpi.sampling.indicator;
   
   import java.util.List;
   
   import org.djunits.unit.LinearDensityUnit;
   import org.djunits.value.vdouble.scalar.LinearDensity;
   import org.djunits.value.vdouble.scalar.Time;
   import org.opentrafficsim.kpi.sampling.Query;
   import org.opentrafficsim.kpi.sampling.TrajectoryGroup;
  
  /**
   * Total travel time divided by the sum of areas (X * T).
   * <p>
   * Copyright (c) 2013-2018 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
   * BSD-style license. See <a href="http://opentrafficsim.org/node/13">OpenTrafficSim License</a>.
   * <p>
   * @version $Revision$, $LastChangedDate$, by $Author$, initial version 16 okt. 2016 <br>
   * @author <a href="http://www.tbm.tudelft.nl/averbraeck">Alexander Verbraeck</a>
   * @author <a href="http://www.tudelft.nl/pknoppers">Peter Knoppers</a>
   * @author <a href="http://www.transport.citg.tudelft.nl">Wouter Schakel</a>
   */
  public class MeanDensity extends AbstractIndicator<LinearDensity>
  {
  
      /** Travel time indicator. */
      private final TotalTravelTime travelTime;
  
      /**
       * @param travelTime travel time indicator
       */
      public MeanDensity(final TotalTravelTime travelTime)
      {
          this.travelTime = travelTime;
      }
  
      /** {@inheritDoc} */
      @Override
      protected LinearDensity calculate(final Query query, final Time startTime, final Time endTime,
              final List<TrajectoryGroup> trajectoryGroups)
      {
          double ttt = this.travelTime.getValue(query, startTime, endTime, trajectoryGroups).si;
          double area = 0;
          for (TrajectoryGroup trajectoryGroup : trajectoryGroups)
          {
              area += trajectoryGroup.getLength().si * (endTime.si - startTime.si);
          }
          return new LinearDensity(ttt / area, LinearDensityUnit.SI);
      }
  
      /** {@inheritDoc} */
      @Override
      public final String toString()
      {
          return "MeanDensity [travelTime=" + this.travelTime + "]";
      }
  
  }