[R] Negative intercept in glm poisson model

[Douglas Bates]

Federico Gherardini wrote:

> I'm trying to fit a glm model using family=poisson(link = "identity"). The 
> problem is that the glm function fits a model with a negative intercept, 
> which sounds like a nonsense to me, being the response a Poisson variable. 

Not really.  The negative intercept is on the scale of the linear 
predictor.  The expected response, which is the exponential of the 
linear predictor, is always positive.