digamma function
digamma(z)
z
positive argument
An object of type numeric. This object is a vector of the same length as x. The output element is :
numeric
psi
frac{d ln(\tau(x))}{dx} = \frac{\tau'(x)}{\tau(x)}. This equal to the output of base::digamma(x)
frac{d ln(\tau(x))}{dx} = \frac{\tau'(x)}{\tau(x)}