id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
11556	hypergeometric constructor's n & r are not consistent with online description!	mchalabi@…	John Maddock	"Hi, at the following URL it reads:

r: number of defective items
n: size of sample

[http://www.boost.org/doc/libs/1_52_0/libs/math/doc/sf_and_dist/html/math_toolkit/dist/dist_ref/dists/hypergeometric_dist.html]

However looking into the constructor of hypergeometric distribution reveals the contrary:

r: sample size
n: number of defective items


{{{
   class hypergeometric_distribution
   {
   public:
      typedef RealType value_type;
      typedef Policy policy_type;

      hypergeometric_distribution(unsigned r, unsigned n, unsigned N) // Constructor.
         : m_n(n), m_N(N), m_r(r)
      {
         static const char* function = ""boost::math::hypergeometric_distribution<%1%>::hypergeometric_distribution"";
         RealType ret;
         check_params(function, &ret);
      }
      // Accessor functions.
      unsigned total()const
      {
         return m_N;
      }

      unsigned defective()const
      {
         return m_n;
      }

      unsigned sample_count()const
      {
         return m_r;
      }

      bool check_params(const char* function, RealType* result)const
      {
         if(m_r > m_N)
         {
            *result = boost::math::policies::raise_domain_error<RealType>(
               function, ""Parameter r out of range: must be <= N but got %1%"", static_cast<RealType>(m_r), Policy());
            return false;
         }
         if(m_n > m_N)
         {
            *result = boost::math::policies::raise_domain_error<RealType>(
               function, ""Parameter n out of range: must be <= N but got %1%"", static_cast<RealType>(m_n), Policy());
            return false;
         }
         return true;
      }
      bool check_x(unsigned x, const char* function, RealType* result)const
      {
         if(x < static_cast<unsigned>((std::max)(0, (int)(m_n + m_r) - (int)(m_N))))
         {
            *result = boost::math::policies::raise_domain_error<RealType>(
               function, ""Random variable out of range: must be > 0 and > m + r - N but got %1%"", static_cast<RealType>(x), Policy());
            return false;
         }
         if(x > (std::min)(m_r, m_n))
         {
            *result = boost::math::policies::raise_domain_error<RealType>(
               function, ""Random variable out of range: must be less than both n and r but got %1%"", static_cast<RealType>(x), Policy());
            return false;
         }
         return true;
      }

   private:
      // Data members:
      unsigned m_n;  // number of ""defective"" items
      unsigned m_N; // number of ""total"" items
      unsigned m_r; // number of items picked

   }; // class hypergeometric_distribution
}}}
"	Bugs	closed	Boost 1.60.0	math	Boost 1.59.0	Problem	fixed	hypergeometric constructor n r	mor.chalabi@…