Log_gamma

Definition:

$log\_gamma = log\_gamma(x)$ evaluates $\ln \Gamma (x)$.x > 0. It is based on Chebyshev expansions.

If x is too large there is a danger of setting overflow so the function evaluation must fail.

For more information please review the s14abc function in the NAG document.

Parameters:

x (input, double)
The argument x of the function.
Constraint: x > 0.0.
$log gamma$ (output, double)
The value of $\ln\Gamma (x)$, x > 0