Negative Binomial Deviance Residual
Parameters : | Y : array-like
mu : array-like
scale : float, optional
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Returns : | resid_dev : array
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Notes
resid_dev = sign(Y-mu) * sqrt(piecewise)
where piecewise is defined as if Y_i = 0: piecewise_i = 2*log(1+alpha*mu)/alpha
if Y_i > 0: piecewise_i = 2*Y*log(Y/\mu)-2/\alpha*(1+\alpha*Y)*log((1+\alpha*Y)/(1+\alpha*\mu))