Digamma function

In mathematics, the digamma function is defined as the logarithmic derivative of the gamma 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 ψ0(x), ψ(0)(x) or Ϝ (the uppercase form of the archaic Greek consonant digamma meaning double-gamma).