I am trying to fit a model with a glm using a tweedie family. I use a index parameter p between 1 and 2 to get a compound Poisson Gamma distribution to fit my data. But I want to use an offset only on the Poisson part of the regression. So my questions are the following ones:
Can this be done and how?
Is it possible to split the two part of the regression (Poisson and Gamma) manually to put the offset only on the Poisson part?
What do you known about the way that a tweedie regression handles an offset?