TruncatedExponentialDiscreteDistribution.h

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//
// File: TruncatedExponentialDiscreteDistribution.h
// Authors:
//   Julien Dutheil
// Created: 2008-01-25 15:24:00
//
 
/*
  Copyright or © or Copr. Bio++ Development Team, (November 17, 2004)
  
  This software is a computer program whose purpose is to provide classes
  for numerical calculus.
  
  This software is governed by the CeCILL license under French law and
  abiding by the rules of distribution of free software. You can use,
  modify and/ or redistribute the software under the terms of the CeCILL
  license as circulated by CEA, CNRS and INRIA at the following URL
  "http://www.cecill.info".
  
  As a counterpart to the access to the source code and rights to copy,
  modify and redistribute granted by the license, users are provided only
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*/
 
#ifndef BPP_NUMERIC_PROB_TRUNCATEDEXPONENTIALDISCRETEDISTRIBUTION_H
#define BPP_NUMERIC_PROB_TRUNCATEDEXPONENTIALDISCRETEDISTRIBUTION_H
 
 
#include "../Constraints.h"
#include "../Random/RandomTools.h"
#include "ExponentialDiscreteDistribution.h"
 
namespace bpp
{
class TruncatedExponentialDiscreteDistribution :
  public AbstractDiscreteDistribution
{
protected:
  double lambda_;
 
  double tp_;
 
  /*
   * Probability of the condition given x < tp_.
   *
   */
 
  double cond_;
 
public:
  TruncatedExponentialDiscreteDistribution(size_t n, double lambda = 1., double truncationPoint = 10);
 
  TruncatedExponentialDiscreteDistribution(const TruncatedExponentialDiscreteDistribution& dist) :
    AbstractDiscreteDistribution(dist),
    lambda_(dist.lambda_),
    tp_(dist.tp_),
    cond_(dist.cond_)
  {}
 
  TruncatedExponentialDiscreteDistribution& operator=(const TruncatedExponentialDiscreteDistribution& dist)
  {
    AbstractDiscreteDistribution::operator=(dist);
    lambda_ = dist.lambda_;
    tp_ = dist.tp_;
    cond_ = dist.cond_;
    return *this;
  }
 
  ~TruncatedExponentialDiscreteDistribution(){}
 
  TruncatedExponentialDiscreteDistribution* clone() const { return new TruncatedExponentialDiscreteDistribution(*this); }
 
public:
  std::string getName() const {return "TruncExponential";}
 
  void fireParameterChanged(const ParameterList& parameters);
 
  double randC() const
  {
    double x = RandomTools::randExponential(1. / getParameterValue("lambda"));
    while (!intMinMax_->isCorrect(x))
      x = RandomTools::randExponential(1. / getParameterValue("lambda"));
 
    return x;
  }
 
  double pProb(double x) const
  {
    if (x >= tp_)
      return 1.;
    else
      return (1. - exp(-lambda_ * x)) / cond_;
  }
 
  double qProb(double x) const
  {
    if (x == 1)
      return tp_;
    else
      return -log(1. - cond_ * x) / lambda_;
  }
 
  double Expectation(double a) const
  {
    if (a < tp_)
      return (1. / lambda_ - exp(-a * lambda_) * (a + 1. / lambda_)) / cond_;
    else
      return (1. / lambda_ - exp(-tp_ * lambda_) * (tp_ + 1. / lambda_)) / cond_;
  }
 
  void restrictToConstraint(const Constraint& c);
};
} // end of namespace bpp.
#endif // BPP_NUMERIC_PROB_TRUNCATEDEXPONENTIALDISCRETEDISTRIBUTION_H