title: How can I do model selection by AIC with a Gamma GLM in R?
body: <p>As the documentation for glm() explains, the aic component of the value returned by glm() is not a valid AIC:</p>
  
  <blockquote>
    <p>For gaussian, Gamma and inverse gaussian
    families the dispersion is estimated from the residual
    deviance, and the number of parameters is the number of
    coefficients plus one.  For a gaussian family the MLE of the
    dispersion is used so this is a valid value of AIC, but for
    Gamma and inverse gaussian families it is not. </p>
  </blockquote>
  
  <p>Thus a valid AIC needs to obtained in some other way.</p>