Logarithmic Derivative

The logarithmic derivative of a function  is defined as the derivative of the logarithm of a function. For example, the digamma function is defined as the logarithmic derivative of the gamma function,

REFERENCES:

Zwillinger, D. (Ed.). "Logarithmic Derivative." §6.11.8 in CRC Standard Mathematical Tables and Formulae. Boca Raton, FL: CRC Press, p. 496, 1995.