[R] Deviance in Zero inflated models

[Achim Zeileis]

On Wed, 3 Apr 2013, Lia McKinnon wrote:

> Dear list,
>
> I am running some zero inflated models and would like to know what the 
> deviance of the models. Unlike running a normal GLM where the deviance 
> is displayed in the summary all that is displayed in a summary of the 
> zero inflated model is the log likelihood.

Zero-inflated models are not associated with a deviance in the GLM sense. 
They are a mixture of two models rather than a single model from an 
exponential family.

Hence, zeroinfl/hurdle in "pscl" reports the log-likelihood but not the 
deviance. Possibly -2 times the likelihood is useful for you - as Ben 
already pointed out.

Best,
Z

> I hope this isn't a read the manual question, and if it is I apologize 
> for wasting your time, but if you could still send me a link of where I 
> might find this information I would be very grateful!
>
> Thank you
> Lia
>
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