/usr/include/shark/Rng/Poisson.h is in libshark-dev 3.0.1+ds1-2ubuntu1.
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*
*
* \brief Implements a poisson distribution.
*
*
*
* \author O. Krause
* \date 2010-01-01
*
*
* \par Copyright 1995-2015 Shark Development Team
*
* <BR><HR>
* This file is part of Shark.
* <http://image.diku.dk/shark/>
*
* Shark is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published
* by the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Shark 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with Shark. If not, see <http://www.gnu.org/licenses/>.
*
*/
#ifndef SHARK_RNG_POISSON_H
#define SHARK_RNG_POISSON_H
#include <shark/Rng/Rng.h>
#include <boost/random.hpp>
#include <boost/random/poisson_distribution.hpp>
namespace shark {
/**
* \brief Implements a Poisson distribution with parameter mean.
*/
template<typename RngType = shark::DefaultRngType>
class Poisson : public boost::variate_generator< RngType*,boost::poisson_distribution<> > {
private:
typedef boost::variate_generator< RngType*,boost::poisson_distribution<> > Base;
public:
/**
* \brief C'tor taking parameter mean as argument. Associates the
* distribution with supplied RNG.
*
*/
Poisson( RngType & rng, double mean = 0.01 )
:Base(&rng,boost::poisson_distribution<>(mean))
{}
/**
* \brief Injects the default sampling operator.
*/
using Base::operator();
/**
* \brief Adjusts the parameter mean and samples the distribution.
* \param [in] mean The new mean.
*/
double operator()(double mean)
{
boost::poisson_distribution<> dist(mean);
return dist(Base::engine());
}
/**
* \brief Accesses the parameter mean.
*/
double mean()const
{
return Base::distribution().mean();
}
/**
* \brief Adjusts the parameter mean.
*/
void mean(double newMean)
{
Base::distribution()=boost::poisson_distribution<>(newMean);
}
/**
* \brief Calculates the probability of x >= 0.
*/
double p(double x)const
{
if(x >= 0.0)
return std::pow(mean(), x) * std::exp(-mean()) / boost::math::factorial<double>(std::size_t(x));
else
return 0;
}
};
}
#endif
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