comparison any/include/boost/math/distributions/gamma.hpp @ 160:cff480c41f97

Add some cross-platform Boost headers

+//  Copyright John Maddock 2006.
+//  Use, modification and distribution are subject to the
+//  Boost Software License, Version 1.0. (See accompanying file
+//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_STATS_GAMMA_HPP
+#define BOOST_STATS_GAMMA_HPP
+
+// http://www.itl.nist.gov/div898/handbook/eda/section3/eda366b.htm
+// http://mathworld.wolfram.com/GammaDistribution.html
+// http://en.wikipedia.org/wiki/Gamma_distribution
+
+#include <boost/math/distributions/fwd.hpp>
+#include <boost/math/special_functions/gamma.hpp>
+#include <boost/math/distributions/detail/common_error_handling.hpp>
+#include <boost/math/distributions/complement.hpp>
+
+#include <utility>
+
+namespace boost{ namespace math
+{
+namespace detail
+{
+
+template <class RealType, class Policy>
+inline bool check_gamma_shape(
+      const char* function,
+      RealType shape,
+      RealType* result, const Policy& pol)
+{
+   if((shape <= 0) || !(boost::math::isfinite)(shape))
+   {
+      *result = policies::raise_domain_error<RealType>(
+         function,
+         "Shape parameter is %1%, but must be > 0 !", shape, pol);
+      return false;
+   }
+   return true;
+}
+
+template <class RealType, class Policy>
+inline bool check_gamma_x(
+      const char* function,
+      RealType const& x,
+      RealType* result, const Policy& pol)
+{
+   if((x < 0) || !(boost::math::isfinite)(x))
+   {
+      *result = policies::raise_domain_error<RealType>(
+         function,
+         "Random variate is %1% but must be >= 0 !", x, pol);
+      return false;
+   }
+   return true;
+}
+
+template <class RealType, class Policy>
+inline bool check_gamma(
+      const char* function,
+      RealType scale,
+      RealType shape,
+      RealType* result, const Policy& pol)
+{
+   return check_scale(function, scale, result, pol) && check_gamma_shape(function, shape, result, pol);
+}
+
+} // namespace detail
+
+template <class RealType = double, class Policy = policies::policy<> >
+class gamma_distribution
+{
+public:
+   typedef RealType value_type;
+   typedef Policy policy_type;
+
+   gamma_distribution(RealType l_shape, RealType l_scale = 1)
+      : m_shape(l_shape), m_scale(l_scale)
+   {
+      RealType result;
+      detail::check_gamma("boost::math::gamma_distribution<%1%>::gamma_distribution", l_scale, l_shape, &result, Policy());
+   }
+
+   RealType shape()const
+   {
+      return m_shape;
+   }
+
+   RealType scale()const
+   {
+      return m_scale;
+   }
+private:
+   //
+   // Data members:
+   //
+   RealType m_shape;     // distribution shape
+   RealType m_scale;     // distribution scale
+};
+
+// NO typedef because of clash with name of gamma function.
+
+template <class RealType, class Policy>
+inline const std::pair<RealType, RealType> range(const gamma_distribution<RealType, Policy>& /* dist */)
+{ // Range of permissible values for random variable x.
+   using boost::math::tools::max_value;
+   return std::pair<RealType, RealType>(static_cast<RealType>(0), max_value<RealType>());
+}
+
+template <class RealType, class Policy>
+inline const std::pair<RealType, RealType> support(const gamma_distribution<RealType, Policy>& /* dist */)
+{ // Range of supported values for random variable x.
+   // This is range where cdf rises from 0 to 1, and outside it, the pdf is zero.
+   using boost::math::tools::max_value;
+   using boost::math::tools::min_value;
+   return std::pair<RealType, RealType>(min_value<RealType>(),  max_value<RealType>());
+}
+
+template <class RealType, class Policy>
+inline RealType pdf(const gamma_distribution<RealType, Policy>& dist, const RealType& x)
+{
+   BOOST_MATH_STD_USING  // for ADL of std functions
+
+   static const char* function = "boost::math::pdf(const gamma_distribution<%1%>&, %1%)";
+
+   RealType shape = dist.shape();
+   RealType scale = dist.scale();
+
+   RealType result = 0;
+   if(false == detail::check_gamma(function, scale, shape, &result, Policy()))
+      return result;
+   if(false == detail::check_gamma_x(function, x, &result, Policy()))
+      return result;
+
+   if(x == 0)
+   {
+      return 0;
+   }
+   result = gamma_p_derivative(shape, x / scale, Policy()) / scale;
+   return result;
+} // pdf
+
+template <class RealType, class Policy>
+inline RealType cdf(const gamma_distribution<RealType, Policy>& dist, const RealType& x)
+{
+   BOOST_MATH_STD_USING  // for ADL of std functions
+
+   static const char* function = "boost::math::cdf(const gamma_distribution<%1%>&, %1%)";
+
+   RealType shape = dist.shape();
+   RealType scale = dist.scale();
+
+   RealType result = 0;
+   if(false == detail::check_gamma(function, scale, shape, &result, Policy()))
+      return result;
+   if(false == detail::check_gamma_x(function, x, &result, Policy()))
+      return result;
+
+   result = boost::math::gamma_p(shape, x / scale, Policy());
+   return result;
+} // cdf
+
+template <class RealType, class Policy>
+inline RealType quantile(const gamma_distribution<RealType, Policy>& dist, const RealType& p)
+{
+   BOOST_MATH_STD_USING  // for ADL of std functions
+
+   static const char* function = "boost::math::quantile(const gamma_distribution<%1%>&, %1%)";
+
+   RealType shape = dist.shape();
+   RealType scale = dist.scale();
+
+   RealType result = 0;
+   if(false == detail::check_gamma(function, scale, shape, &result, Policy()))
+      return result;
+   if(false == detail::check_probability(function, p, &result, Policy()))
+      return result;
+
+   if(p == 1)
+      return policies::raise_overflow_error<RealType>(function, 0, Policy());
+
+   result = gamma_p_inv(shape, p, Policy()) * scale;
+
+   return result;
+}
+
+template <class RealType, class Policy>
+inline RealType cdf(const complemented2_type<gamma_distribution<RealType, Policy>, RealType>& c)
+{
+   BOOST_MATH_STD_USING  // for ADL of std functions
+
+   static const char* function = "boost::math::quantile(const gamma_distribution<%1%>&, %1%)";
+
+   RealType shape = c.dist.shape();
+   RealType scale = c.dist.scale();
+
+   RealType result = 0;
+   if(false == detail::check_gamma(function, scale, shape, &result, Policy()))
+      return result;
+   if(false == detail::check_gamma_x(function, c.param, &result, Policy()))
+      return result;
+
+   result = gamma_q(shape, c.param / scale, Policy());
+
+   return result;
+}
+
+template <class RealType, class Policy>
+inline RealType quantile(const complemented2_type<gamma_distribution<RealType, Policy>, RealType>& c)
+{
+   BOOST_MATH_STD_USING  // for ADL of std functions
+
+   static const char* function = "boost::math::quantile(const gamma_distribution<%1%>&, %1%)";
+
+   RealType shape = c.dist.shape();
+   RealType scale = c.dist.scale();
+   RealType q = c.param;
+
+   RealType result = 0;
+   if(false == detail::check_gamma(function, scale, shape, &result, Policy()))
+      return result;
+   if(false == detail::check_probability(function, q, &result, Policy()))
+      return result;
+
+   if(q == 0)
+      return policies::raise_overflow_error<RealType>(function, 0, Policy());
+
+   result = gamma_q_inv(shape, q, Policy()) * scale;
+
+   return result;
+}
+
+template <class RealType, class Policy>
+inline RealType mean(const gamma_distribution<RealType, Policy>& dist)
+{
+   BOOST_MATH_STD_USING  // for ADL of std functions
+
+   static const char* function = "boost::math::mean(const gamma_distribution<%1%>&)";
+
+   RealType shape = dist.shape();
+   RealType scale = dist.scale();
+
+   RealType result = 0;
+   if(false == detail::check_gamma(function, scale, shape, &result, Policy()))
+      return result;
+
+   result = shape * scale;
+   return result;
+}
+
+template <class RealType, class Policy>
+inline RealType variance(const gamma_distribution<RealType, Policy>& dist)
+{
+   BOOST_MATH_STD_USING  // for ADL of std functions
+
+   static const char* function = "boost::math::variance(const gamma_distribution<%1%>&)";
+
+   RealType shape = dist.shape();
+   RealType scale = dist.scale();
+
+   RealType result = 0;
+   if(false == detail::check_gamma(function, scale, shape, &result, Policy()))
+      return result;
+
+   result = shape * scale * scale;
+   return result;
+}
+
+template <class RealType, class Policy>
+inline RealType mode(const gamma_distribution<RealType, Policy>& dist)
+{
+   BOOST_MATH_STD_USING  // for ADL of std functions
+
+   static const char* function = "boost::math::mode(const gamma_distribution<%1%>&)";
+
+   RealType shape = dist.shape();
+   RealType scale = dist.scale();
+
+   RealType result = 0;
+   if(false == detail::check_gamma(function, scale, shape, &result, Policy()))
+      return result;
+
+   if(shape < 1)
+      return policies::raise_domain_error<RealType>(
+         function,
+         "The mode of the gamma distribution is only defined for values of the shape parameter >= 1, but got %1%.",
+         shape, Policy());
+
+   result = (shape - 1) * scale;
+   return result;
+}
+
+//template <class RealType, class Policy>
+//inline RealType median(const gamma_distribution<RealType, Policy>& dist)
+//{  // Rely on default definition in derived accessors.
+//}
+
+template <class RealType, class Policy>
+inline RealType skewness(const gamma_distribution<RealType, Policy>& dist)
+{
+   BOOST_MATH_STD_USING  // for ADL of std functions
+
+   static const char* function = "boost::math::skewness(const gamma_distribution<%1%>&)";
+
+   RealType shape = dist.shape();
+   RealType scale = dist.scale();
+
+   RealType result = 0;
+   if(false == detail::check_gamma(function, scale, shape, &result, Policy()))
+      return result;
+
+   result = 2 / sqrt(shape);
+   return result;
+}
+
+template <class RealType, class Policy>
+inline RealType kurtosis_excess(const gamma_distribution<RealType, Policy>& dist)
+{
+   BOOST_MATH_STD_USING  // for ADL of std functions
+
+   static const char* function = "boost::math::kurtosis_excess(const gamma_distribution<%1%>&)";
+
+   RealType shape = dist.shape();
+   RealType scale = dist.scale();
+
+   RealType result = 0;
+   if(false == detail::check_gamma(function, scale, shape, &result, Policy()))
+      return result;
+
+   result = 6 / shape;
+   return result;
+}
+
+template <class RealType, class Policy>
+inline RealType kurtosis(const gamma_distribution<RealType, Policy>& dist)
+{
+   return kurtosis_excess(dist) + 3;
+}
+
+} // namespace math
+} // namespace boost
+
+// This include must be at the end, *after* the accessors
+// for this distribution have been defined, in order to
+// keep compilers that support two-phase lookup happy.
+#include <boost/math/distributions/detail/derived_accessors.hpp>
+
+#endif // BOOST_STATS_GAMMA_HPP
+
+