gammaincReg

constexpr double gammaincReg(const double a, const double x) noexcept: Evaluates the regularized lower incomplete gamma function [1].

Parameters

const double a

A real number.

const double x

A real number.

Returns

double

A real number.

This regularized version is defined as:

\[P(a, x) = \frac{\gamma(a, x)}{\Gamma(a)}\]

Example

double a = 1;
double x = 1;
std::cout << gammaincReg(a, x) << "\n";

Output:

0.632121

References