[R] Help with nonlinear regression of binomial data

[Harborne, Alastair]

Hi all,
I have a manuscript nearly ready to go looking at a factorial analysis (inside and outside a Caribbean marine reserve) of how the biomass of predatory fish affects the proportion of survey transects containing urchins (more predators leads to fewer urchins). I would like to add some regression analysis, but my linear models with binomial errors are overdispersed because the data are nonlinear (negative power by the look of it). I have spent some time playing with gnlr but have realised that it is unlikely that I will be able to get the analysis to a publishable standard. If anyone is interested in working with me to complete this analysis I would happily include them as a co-author on the paper. The data are appended below in case anyone wants to see it.
Thanks,
Alastair

Pred_biomass            proportion of transects with urchins
372.25                  0.28571
173.66                  0.14286
205.00                  0.28571
3436.77                 0.00000
862.54                  0.00000
387.82                  0.00000
385.50                  0.00000
345.83                  0.28571
132.61                  1.00000

- Note there seems to be an additional wrinkle as the biomass data are difficult to normalise.
__

Dr Alastair Harborne

Marine Spatial Ecology Lab
School of Biosciences
Hatherly Laboratory
University of Exeter, Prince of Wales Road
Exeter, EX4 4PS, UK

Phone: 01392-263784
Fax: 01392-263700
Skype name: al_harborne
Group website: http://www.ex.ac.uk/msel
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