Package nl.tudelft.simulation.jstats.distributions

Class DistGamma

java.lang.Object
nl.tudelft.simulation.jstats.distributions.Dist
nl.tudelft.simulation.jstats.distributions.DistContinuous
nl.tudelft.simulation.jstats.distributions.DistGamma
All Implemented Interfaces:
Serializable
public class DistGamma extends DistContinuous
The Gamma distribution. For more information on this distribution see https://mathworld.wolfram.com/GammaDistribution.html
The parameters are not rate-related, but average-related, so the mean is shape*scale (or αθ), and the variance is αθ2.

Copyright (c) 2002-2024 Delft University of Technology, Jaffalaan 5, 2628 BX Delft, the Netherlands. All rights reserved. See for project information https://simulation.tudelft.nl. The DSOL project is distributed under a three-clause BSD-style license, which can be found at https://https://simulation.tudelft.nl/dsol/docs/latest/license.html.

Author:
Peter Jacobs , Alexander Verbraeck
See Also:

  • Constructor Details

    • DistGamma

      public DistGamma(StreamInterface stream, double shape, double scale)
      constructs a new gamma distribution. The gamma distribution represents the time to complete some task, e.g. customer service or machine repair. The parameters are not rate-related, but average-related, so the mean is shape*scale (or αθ or kθ), and the variance is αθ2.
      Parameters:
      stream - StreamInterface; the random number stream
      shape - double; is the shape parameter > 0, also known as α or k
      scale - double; is the scale parameter> 0, also known as θ
      Throws:
      IllegalArgumentException - when shape <= 0.0 or scale <= 0.0

  • Method Details

    • draw

      public double draw()
      draws the next stream value according to the probability of this this distribution.
      Specified by:
      draw in class DistContinuous
      Returns:
      the next double value drawn.

    • getProbabilityDensity

      public double getProbabilityDensity(double x)
      returns the probability density value of a value x.
      Specified by:
      getProbabilityDensity in class DistContinuous
      Parameters:
      x - double; the value for which the density function needs to be calculated
      Returns:
      double; the probability density for value x

    • getShape

      public double getShape()
      Returns:
      alpha

    • getScale

      public double getScale()
      Returns:
      beta

    • toString

      public String toString()
      Overrides:
      toString in class Object