On 2/25/2016 1:53 PM, Katharine Miller - NOAA Federal wrote:
The dependent variable is catch per unit effort (CPUE), and the independent variable is the the tributary (Trib_cat). CPUE is derived from the fish counts divided by the effort, so the response is not a count per se, but I think the negative binomial is appropriate because of the large numbers of zeros in the dependent variable.
You probably shouldn't be dividing by effort -- better to use effort as an offset (but I'm not certain that glm.nb supports that)
For the excess zeros, consider using a zero-inflated NB or a hurdle NB model from the pscl package or countreg package (only on R-Forge) -Michael ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
