26 Numerics library [numerics]
26.5 Random number generation [rand]
26.5.8 Random number distribution class templates [rand.dist]
26.5.8.5 Normal distributions [rand.dist.norm]
26.5.8.5.3 Class template chi_squared_distribution [rand.dist.norm.chisq]
A chi_squared_distribution random number distribution
produces random numbers x>0
distributed according to
the probability density function
![\[%
p(x\,|\,n)
= \frac{ x^{(n/2)-1} \cdot e^{-x/2}}
{\Gamma(n/2) \cdot 2^{n/2}}
\; \mbox{.}
\]](math/6635143828116624469.png)
template<class RealType = double>
class chi_squared_distribution{
public:
// types
typedef RealType result_type;
typedef unspecified param_type;
// constructor and reset functions
explicit chi_squared_distribution(RealType n = 1);
explicit chi_squared_distribution(const param_type& parm);
void reset();
// generating functions
template<class URNG>
result_type operator()(URNG& g);
template<class URNG>
result_type operator()(URNG& g, 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;
};
Requires: 0 < n .
Effects: Constructs a chi_squared_distribution object; n corresponds to the parameter of the distribution.
Returns: The value of the n parameter with which the object was constructed.