[R-sig-eco] Low counts

[Tore Chr Michaelsen]

Dear members;

1) I have fitted a glm to count data (using quasipoisson to correct for
disp.). In the final model, the relationship between Res and Fitted (i.e.
the line going through the plot) and QQ looks fine, but I am worried that
low count (one to five) could violate some assumption of the glm/poisson:
Although the line in the Res vs Fitted plot looks nice, the values show a
clear pattern (five diagonal lines = the counts). Crawley/R book says it
should look like the sky at night with no patterns. I assume patterns are
not visible with large counts (e.g. 0-100), but highly visible with low
counts as in this case. I still assume this is reason for some concern about
the model, or is the concern not justified?

2) Any recommendations on literature regarding model inspection in R.

Thank you for reading this mail!

Best wishes;
Tore