Hi Far from being an expert in this field I assume the answer is that it is included in intercept term. It has something to do with contrasts specification, but its usage is above my modelling knowledge.
You could try to see what ?contrasts tells you. Regards Petr you can > > Hello, > I’m using zero-inflated Poisson regression via the zeroinfl() function to > analyze data on seed-set of plants, but for some reason, I don’t seem to be > getting the output for all three levels of my two categorical predictors. > > More about my data and model: > My response variable is the number of viable seeds (AVInt), and my two > categorical predictors are elevation (Elev) and Treatment (Treatment). Elev > has three levels: 01-Low, 02-Mid, and 03-High; Treatment also has three > possibilities: B, F, or O. > > Because the response variable (AVInt) is zero-inflated and > Poisson-distributed, I’m using zeroinfl() under the pcsl library as an > alternative to factorial ANOVA (I’ve also tried the zero-inflated negative > binomial). This is early in my data-analysis, but I will likely incorporate > additional categorical and continuous predictors at a later time. > > This gives me the following model: > > zipclay=zeroinfl(AVInt ~ Elev + Treatment) > > So running the model, I have: > > zipclay=zeroinfl(AVInt ~ Elev + Treatment) > > summary(zipclay) > > Call: > zeroinfl(formula = AVInt ~ Elev + Treatment) > > Pearson residuals: > Min 1Q Median 3Q Max > -1.1958 -0.5612 -0.3764 0.2704 5.5130 > > Count model coefficients (poisson with log link): > Estimate Std. Error z value Pr(>|z|) > (Intercept) -0.2035 0.3435 -0.592 0.55368 > Elev02-Mid 0.3937 0.1806 2.180 0.02923 * > Elev03-High 0.1635 0.1792 0.912 0.36159 > TreatmentF 1.0026 0.3305 3.033 0.00242 ** > TreatmentO 0.5915 0.3293 1.796 0.07244 . > > Zero-inflation model coefficients (binomial with logit link): > Estimate Std. Error z value Pr(>|z|) > (Intercept) 1.6086 0.5080 3.167 0.00154 ** > Elev02-Mid -0.3813 0.4345 -0.878 0.38020 > Elev03-High -0.9512 0.4532 -2.099 0.03584 * > TreatmentF -0.9774 0.4690 -2.084 0.03718 * > TreatmentO -3.0242 0.6561 -4.609 4.05e-06 *** > --- > Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 > > Number of iterations in BFGS optimization: 16 > Log-likelihood: -363.2 on 10 Df > > So my question is, where did my "Elev01-Low" and "TreatmentB" go?? Why > aren't they appearing in the output table? > > Any insight would be greatly appreciated! > > - Jason > > > > -- > View this message in context: http://r.789695.n4.nabble.com/Can-t-find- > all-levels-of-categorical-predictors-in-output-of-zeroinfl-tp4444214p4444214.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > [email protected] 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. ______________________________________________ [email protected] 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.
