search for: abovegroundbiomass

Hello everyone I am currently trying to conduct analysis of my graduate thesis data using a mixed effects model and I have reached an impass. When I try to conduct a multiple comparison, I get an error (See below): > fm3<- lme(abovegroundbiomass.m.2~medium*amelioration*fertilizer*treatment, random=~1|block/medium/amelioration/fertilizer) > tukeytest<-glht(fm3, linfct=mcp(treatment="Tukey")) Error in contrMat(table(mf[[nm]]), type = types[pm]) : less than two groups I wonder if anyone could help me interpret this error...

...vided again into two subplots (fertilizer - yes or no). Then for eachfertilizer subplot, the area was divided into 7 seeding treatments (treatments). I have transformed my data to meet model assumptions and simplified my model using stepwise elimination. Here is my minimal model: fm13<- lme(sqrt(abovegroundbiomass.m.2)~amelioration+fertilizer+treatment,random=~1|block, method="ML",na.action = na.omit) Here is a summary output: summary(fm13)$tTable Value Std.Error DF t-value p-value (Intercept) 1.619661...