Dear list,

i'm checking the residuals plots of a gam model after a processus of model
selection. I found the "best" model, all my terms are significant, the
r-square and the deviance explained are good, but I have strange residuals
plots:

http://dl.dropbox.com/u/1169100/gam.check.png
http://dl.dropbox.com/u/1169100/residuals_vs_fitted.png

The curve is caused by the zeroes in my data.

I've also plotted each explanatory variables included in the model
against residuals
and everything looks fine.

Is this curve does not allow me to accept this model?

Does the use of an other family (eg negbin) would be the solution for fixing
this problem? Currently I use the poisson family  (and quasipoisson). I have
a lot of 0 in my response variable, almost 65 %.... Should I use a specific
function that allows me to use zero-inflated data??

Kind regards,

Sam

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