'Starting value for mu in the IRLS algorithm.
Parameters
y : array
The untransformed response variable.
Returns
mu_0 : array
The first guess on the transformed response variable.
Notes
.. math::
\mu_0 = (Y + \overline{Y})/2
Notes
Only the Binomial family takes a different initial value.'

def starting_mu(self, y):

    return ((y + y.mean()) / 2.0)
