alternative parametrization of the negative binomial in scipy

Question

In scipy the negative binomial distribution is defined as:

nbinom.pmf(k) = choose(k+n-1, n-1) * p**n * (1-p)**k

This is the common definition,

Answer 1

The Wikipedia page you linked given a precise formula for p and r in terms of mu and sigma, see the very last bullet item in the Alternative parametrization section,https://en.m.wikipedia.org/wiki/Negative_binomial_distribution#Alternative_formulations