In mathematics, the digamma function is defined as the logarithmic derivative of the gamma function: {\displaystyle \psi ={\frac {d}{dx}}\ln {\big }={\frac {\Gamma '}{\Gamma }}\sim \ln {x}-{\frac {1}{2x}}.} It is the first of the polygamma functions.

What is a digamma function?

In mathematics, the digamma function is defined as the logarithmic derivative of the gamma function: It is the first of the polygamma functions. The digamma function is often denoted as. or Ϝ (the uppercase form of the archaic Greek consonant digamma meaning double-gamma).

What is the meaning of poly gamma?

In mathematics, the polygamma function of order m is a meromorphic function on the complex numbers ℂ defined as the (m + 1)th derivative of the logarithm of the gamma function: Thus. holds where ψ(z) is the digamma function and Γ(z) is the gamma function.