/usr/include/shark/Rng/Weibull.h is in libshark-dev 3.0.1+ds1-2ubuntu1.
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*
*
* \brief Implements a Weibull 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_WEIBULL_H
#define SHARK_RNG_WEIBULL_H
#include <shark/Core/Exception.h>
#include <shark/Rng/Rng.h>
#include <boost/random.hpp>
#include <boost/random/uniform_01.hpp>
#include <cmath>
#include <istream>
namespace shark{
/// \brief Weibull distribution.
template<class RealType = double>
class Weibull_distribution
{
public:
typedef RealType input_type;
typedef RealType result_type;
explicit Weibull_distribution(RealType alpha,RealType beta)
:alpha_(alpha),beta_(beta)
{}
RealType alpha() const
{
return alpha_;
}
RealType beta()const
{
return beta_;
}
void reset() { }
template<class Engine>
result_type operator()(Engine& eng)
{
double uni = boost::uniform_01<RealType>()(eng);
return std::pow(-beta_ * std::log(1. - uni), 1 / alpha_);
}
template<class CharT, class Traits>
friend std::basic_ostream<CharT,Traits>&
operator<<(std::basic_ostream<CharT,Traits>& os, const Weibull_distribution& d)
{
os << d.alpha_;
os << d.beta_;
return os;
}
template<class CharT, class Traits>
friend std::basic_istream<CharT,Traits>&
operator>>(std::basic_istream<CharT,Traits>& is, Weibull_distribution& d)
{
is >> d.alpha_;
is >> d.beta_;
return is;
}
private:
RealType alpha_;
RealType beta_;
};
/// \brief Weibull distributed random variable.
template<typename RngType = shark::DefaultRngType>
class Weibull:public boost::variate_generator<RngType*,Weibull_distribution<> >
{
private:
typedef boost::variate_generator<RngType*,Weibull_distribution<> > Base;
public:
Weibull( RngType & rng, double alpha = 1, double beta = 1 )
:Base(&rng,Weibull_distribution<>(alpha,beta))
{}
using Base::operator();
double operator()(double alpha,double beta)
{
Weibull_distribution<> dist(alpha,beta);
return dist(Base::engine());
}
double alpha()const
{
return Base::distribution().alpha();
}
double beta()const
{
return Base::distribution().beta();
}
void alpha(double newAlpha)
{
Base::distribution()=Weibull_distribution<>(newAlpha,beta());
}
void vbeta(double newBeta)
{
Base::distribution()=Weibull_distribution<>(alpha(),newBeta);
}
double p(double x)const
{
if (x <= 0)
{
throw SHARKEXCEPTION("Weibull distribution not defined for x <= 0");
}
return alpha() / beta() * exp(-pow(x / beta(), alpha())) * pow(x / beta(), alpha() - 1.);
}
};
}
#endif
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