Hi everyone, I am trying to construct a glm and am running into a couple of questions.
The data set I am using consists of 6 categories for the response and 6 independent predictors representing nutrient concentrations at sample point locations. Ultimately I'd like to use the probabilities for each response category in a simulation model such that these probabilities are used to define a realized ecological niche. When I try the following it works for a single response. Typha.glm <- glm(fwc$VegType == "Cattail" ~ fwc$TP + fwc$TC + fwc$TN + fwc$BD + fwc$LOI + fwc$Total_Mg, family = poisson) But if I try this without specifying a specific VegType it fails. plants.glm <- glm(fwc$VegType ~ fwc$TP + fwc$TC + fwc$TN + fwc$BD + fwc$LOI + fwc$Total_Mg, family = poisson) Error in y + 0.1 : non-numeric argument to binary operator In addition: Warning message: In model.matrix.default(mt, mf, contrasts) : variable 'fwc$VegType' converted to a factor My questions are: 1. How can I extract the probability of the VegType for different concentrations of each of the independent parameters? 2. Do I need to run this model extracting for a specific VegType each time or is there a way to run the glm for each VegType in one statement? 3. I've experimented with binning each of the nutrient values to establish frequency values for each VegType, but am uncertain how to reconstruct that data into a common data set that can be submitted to the glm. Is this step even necessary ? Running on Windows XP R 2.10.1 Thanks and Much Appreciated Steve Steve Friedman Ph. D. Spatial Statistical Analyst Everglades and Dry Tortugas National Park 950 N Krome Ave (3rd Floor) Homestead, Florida 33034 steve_fried...@nps.gov Office (305) 224 - 4282 Fax (305) 224 - 4147 ______________________________________________ R-help@r-project.org mailing list 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.
