polygamma

Polygamma function ψ^(k)(x).

Syntax

v = polygamma(k, x)

Description

Returns the k-th derivative of the digamma function ψ(x) = d/dx ln(Γ(x)). With k = 0, returns ψ(x) itself; k = 1 gives the trigamma function, etc.

Example

polygamma(0, 1)        % ≈ -0.5772 (Euler-Mascheroni constant)

See also

• gamma — Gamma function Γ(x).
• gammaln — Natural logarithm of the gamma function, ln(|Γ(x)|).