'Initialize the response variable.
Parameters
endog : array
Endogenous response variable
freq_weights : array
1d array of frequency weights
Returns
If `endog` is binary, returns `endog`
If `endog` is a 2d array, then the input is assumed to be in the format
(successes, failures) and
successes/(success + failures) is returned.  And n is set to
successes + failures.'

def initialize(self, endog, freq_weights):

    if ((endog.ndim > 1) and (endog.shape[1] > 1)):
        y = endog[:, 0]
        self.n = endog.sum(1)
        return (((y * 1.0) / self.n), self.n)
    else:
        return (endog, np.ones(endog.shape[0]))
