{

cout << "Example using Inverse chi squared distribution to find df. " << endl;

try

{

cout.precision(std::numeric_limits<double>::max_digits10); //

int i = std::numeric_limits<double>::max_digits10;

cout << "Show all potentially significant decimal digits std::numeric_limits<double>::max_digits10 = " << i << endl;

cout.precision(3);

double nu = 10.;

double scale1 = 1./ nu; // 1st definition sigma^2 = 1/df;

double scale2 = 1.; // 2nd definition sigma^2 = 1

inverse_chi_squared sichsq(nu, 1/nu); // Explicitly scaled to default scale = 1/df.

inverse_chi_squared ichsq(nu); // Implicitly scaled to default scale = 1/df.

// Try degrees of freedom estimator

//double df = chi_squared::find_degrees_of_freedom(-diff, alpha[i], alpha[i], variance);

cout << "ichsq.degrees_of_freedom() = " << ichsq.degrees_of_freedom() << endl;

double diff = 0.5; // difference from variance to detect (delta).

double variance = 1.; // true variance

double alpha = 0.9;

double beta = 0.9;

cout << "diff = " << diff

<< ", variance = " << variance << ", ratio = " << diff/variance

<< ", alpha = " << alpha << ", beta = " << beta << endl;

using boost::math::detail::inverse_chi_square_df_estimator;

using boost::math::policies::default_policy;

inverse_chi_square_df_estimator<> a_df(alpha, beta, variance, diff);

cout << "df est" << endl;

for (double df = 1; df < 3; df += 0.1)

{

double est_df = a_df(1);

cout << df << " " << a_df(df) << endl;

}

//template <class F, class T, class Tol, class Policy>std::pair<T, T>

// bracket_and_solve_root(F f, const T& guess, T factor, bool rising, Tol tol, boost::uintmax_t& max_iter, const Policy& pol)

//double df = inverse_chi_squared_distribution<>::find_degrees_of_freedom(diff, alpha, beta, variance, 0);

double df = inverse_chi_squared::find_degrees_of_freedom(diff, alpha, beta, variance, 100);

cout << df << endl;

}

catch(const std::exception& e)

{ // Always useful to include try & catch blocks because default policies

// are to throw exceptions on arguments that cause errors like underflow, overflow.

// Lacking try & catch blocks, the program will abort without a message below,

// which may give some helpful clues as to the cause of the exception.

std::cout <<

"\n""Message from thrown exception was:\n " << e.what() << std::endl;

}

return 0;