id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
9834,Negative Binomial Distribution: degenerate cases,HS <tan@…>,John Maddock,"In the following calculations (please see code included below), the 4 results cannot be all correct at the same time.

Also, if one will to uncomment the last block of code, one would find that its calculation would fail.

'''Thoughts:'''
* Now when the probability of ""success"" p0 (you used p in your documentation) is 1, shouldn't the value of the corresponding random variable be simply 0?  If so, shouldn't the quantiles at p=0 and p=1 be both at 0?

* Similarly, when p0 is 0, I would think it is quite ""natural"" to set/define the corresponding random variable to be one with mass 1 at infinity ... no need to work so hard to search for the zero as the error to the final calculation shows.

Thank you.[[br]]
HS

P.S.  Please copy the included code to a test.cpp and then build with g++ -o test test.cpp.

P.ps.  If the evaluation policy will to change to ignore the error, it ''appears'' that the calculation never complete.  Can something be done to prevent this?  Suggestions?

{{{
#define BOOST_MATH_DOMAIN_ERROR_POLICY ignore_error
#define BOOST_MATH_OVERFLOW_ERROR_POLICY ignore_error
// #define BOOST_MATH_EVALUATION_ERROR_POLICY ignore_error
#define BOOST_MATH_DISCRETE_QUANTILE_POLICY integer_round_up

#include <cstdlib>
#include <cstdio>

#include <boost/math/distributions/negative_binomial.hpp>

int main()
{
   double _r0 = 3.0;
   double _p0 = 1.0;

   boost::math::negative_binomial_distribution<> _dist( _r0, _p0 );

   std::printf(
         ""\n""
         ""   r = %g\n""
         ""   p = %g\n\n"",
         _r0,
         _p0 );

   std::printf(
         ""   Quantile(%g;upperTail=false) = %g\n"",
         1.0,
         boost::math::quantile( _dist, 1.0 ) );

   std::printf(
         ""   Quantile(%g;upperTail=true) = %g\n\n"",
         1.0,
         boost::math::quantile(
            boost::math::complement(
               _dist,
               1.0 ) ) );

   std::printf(
         ""   Quantile(%g;upperTail=false) = %g\n"",
         0.0,
         boost::math::quantile( _dist, 0.0 ) );

   std::printf(
         ""   Quantile(%g;upperTail=true) = %g\n\n"",
         0.0,
         boost::math::quantile(
            boost::math::complement(
               _dist,
               0.0 ) ) );

   /*
   {
      _p0 = 0.0;

      boost::math::negative_binomial_distribution<> _dist( _r0, _p0 );

      std::printf(
            ""\n""
            ""   r = %g\n""
            ""   p = %g\n\n"",
            _r0,
            _p0 );

      std::printf(
            ""   Quantile(%g;upperTail=false) = %g\n"",
            0.32,
            boost::math::quantile( _dist, 0.32 ) );
   }
   */

   return EXIT_SUCCESS;
}
}}}

",Feature Requests,closed,To Be Determined,math,Boost Development Trunk,Problem,fixed,,