digamma
-
constexpr Complex digamma(const Complex &z) noexcept
Evaluates the digamma function [1] for a complex input. It has the same definition as the psi function.
Parameters
- const Complex &z
A complex number.
Returns
- type Complex
A complex number.
The digamma function is the derivative of the natural log of the gamma function. It is defined as:
\[\psi(z) = \frac{\Gamma'(z)}{\Gamma(z)}\]
Example
Complex z = 1.0 + 1_j;
std::cout << digamma(z) << "\n";
Output:
0.0946503 + 1.07667j
References