student_t_distribution Class

The latest version of this topic can be found at student_t_distribution Class.

Generates a Student's t-distribution.

Syntax

class student_t_distribution  
   {  
   public:  // types  
   typedef RealType result_type;  
   struct param_type;  // constructor and reset functions  
   explicit student_t_distribution(RealType n = 1.0);
   explicit student_t_distribution(const param_type& parm);
   void reset();
   // generating functions  
   template <class URNG>  
   result_type operator()(URNG& gen);
   template <class URNG>  
   result_type operator()(URNG& gen, const param_type& parm);
   // property functions  
   RealType n() const;
   param_type param() const;
   void param(const param_type& parm);
   result_type min() const;
   result_type max() const;
   };  

Parameters

RealType
The floating-point result type, defaults to double. For possible types, see <random>.

Remarks

The template class describes a distribution that produces values of a user-specified integral type, or type double if none is provided, distributed according to the Student's t-Distribution. The following table links to articles about individual members.

The property function n() returns the value for the stored distribution parameter n.

For more information about distribution classes and their members, see <random>.

For detailed information about the Student's t-distribution, see the Wolfram MathWorld article Students t-Distribution.

Example

// compile with: /EHsc /W4  
#include <random>   
#include <iostream>  
#include <iomanip>  
#include <string>  
#include <map>  
  
void test(const double n, const int s) {  
  
    // uncomment to use a non-deterministic generator  
    //    std::random_device gen;  
    std::mt19937 gen(1701);  
  
    std::student_t_distribution<> distr(n);  
  
    std::cout << std::endl;  
    std::cout << "min() == " << distr.min() << std::endl;  
    std::cout << "max() == " << distr.max() << std::endl;  
    std::cout << "n() == " << std::fixed << std::setw(11) << std::setprecision(10) << distr.n() << std::endl;  
  
    // generate the distribution as a histogram  
    std::map<double, int> histogram;  
    for (int i = 0; i < s; ++i) {  
        ++histogram[distr(gen)];  
    }  
  
    // print results  
    std::cout << "Distribution for " << s << " samples:" << std::endl;  
    int counter = 0;  
    for (const auto& elem : histogram) {  
        std::cout << std::fixed << std::setw(11) << ++counter << ": "  
            << std::setw(14) << std::setprecision(10) << elem.first << std::endl;  
    }  
    std::cout << std::endl;  
}  
  
int main()  
{  
    double n_dist = 0.5;  
    int samples = 10;  
  
    std::cout << "Use CTRL-Z to bypass data entry and run using default values." << std::endl;  
    std::cout << "Enter a floating point value for the 'n' distribution parameter (must be greater than zero): ";  
    std::cin >> n_dist;  
    std::cout << "Enter an integer value for the sample count: ";  
    std::cin >> samples;  
  
    test(n_dist, samples);  
}  
  

Output

Use CTRL-Z to bypass data entry and run using default values.  
Enter a floating point value for the 'n' distribution parameter (must be greater than zero): 1  
Enter an integer value for the sample count: 10  
 
min() == -1.79769e+308  
max() == 1.79769e+308  
n() == 1.0000000000  
Distribution for 10 samples:  
    1: -1.3084956212  
    2: -1.0899518684  
    3: -0.9568771388  
    4: -0.9372088821  
    5: -0.7381334669  
    6: -0.2488074854  
    7: -0.2028714601  
    8: 1.4013074495  
    9: 5.3244792236  
    10: 92.7084335614  

Requirements

Header: <random>

Namespace: std

student_t_distribution::student_t_distribution

Constructs the distribution.

explicit student_t_distribution(RealType n = 1.0);

 
explicit student_t_distribution(const param_type& parm);

Parameters

n
The n distribution parameter.

parm
The parameter package used to construct the distribution.

Remarks

Precondition: 0.0 < n

The first constructor constructs an object whose stored n value holds the value n.

The second constructor constructs an object whose stored parameters are initialized from parm. You can obtain and set the current parameters of an existing distribution by calling the param() member function.

student_t_distribution::param_type

Stores all the parameters of the distribution.

struct param_type {  
   typedef student_t_distribution<RealType> distribution_type;  
   param_type(RealType n = 1.0);
   RealType n() const;
   .....  
   bool operator==(const param_type& right) const;
   bool operator!=(const param_type& right) const;
   };  

Parameters

See parent topic student_t_distribution Class.

Remarks

Precondition: 0.0 < n

This structure can be passed to the distribution's class constructor at instantiation, to the param() member function to set the stored parameters of an existing distribution, and to operator() to be used in place of the stored parameters.

See Also

<random>