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.


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