In mathematics, the digamma function is defined as the logarithmic derivative of the gamma function: ψ ( z ) = d d z ln Γ ( z ) = Γ ′ ( z ) Γ ( z ) . {\displaystyle \psi (z)={\frac {d}{dz}}\ln \Gamma (z)={\frac {\Gamma '(z)}{\Gamma (z)}}.} It is the first of the polygamma functions.
In mathematics, the digamma function is defined as the logarithmic derivative of the gamma function: ψ ( z ) = d d z ln Γ ( z ) = Γ ′ ( z ) Γ ( z ) . {\displaystyle \psi (z)={\frac {d}{dz}}\ln \Gamma (z)={\frac {\Gamma '(z)}{\Gamma (z)}}.} It is the first of the polygamma functions.
Source: Wikipedia "Digamma function" · CC BY-SA 4.0
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