# std::chi_squared_distribution

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< cpp‎ | numeric‎ | random

Defined in header `<random>` |  |
template< class RealType = double > class chi_squared_distribution; |  | (since C++11)

The `chi_squared_distribution` produces random numbers x>0 according to the Chi-squared distribution:

  f(x;n) =

  x(n/2)-1 e-x/2
  Γ(n/2) 2n/2

Γ is the Gamma function (See also std::tgamma) and n are the degrees of freedom (default 1).

`std::chi_squared_distribution` satisfies all requirements of `RandomNumberDistribution`

### Template parameters

RealType | - | The result type generated by the generator. The effect is undefined if this is not one of float, double, or long double.

### Member types

Member type | Definition
`result_type` | RealType
`param_type` | the type of the parameter set, see `RandomNumberDistribution`.

### Member functions

(constructor) | constructs new distribution (public member function)
reset | resets the internal state of the distribution (public member function)

##### Generation

operator() | generates the next random number in the distribution (public member function)

##### Characteristics

n | returns the degrees of freedom (n) distribution parameter (public member function)
param | gets or sets the distribution parameter object (public member function)
min | returns the minimum potentially generated value (public member function)
max | returns the maximum potentially generated value (public member function)

### Non-member functions

operator==operator!= | compares two distribution objects (function)
operator<<operator>> | performs stream input and output on pseudo-random number distribution (function template)

### Example

| This section is incomplete Reason: no example

### External links

- Weisstein, Eric W. "Chi-Squared Distribution." From MathWorld--A Wolfram Web Resource.
- Chi-squared distribution. From Wikipedia.

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