
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. Many thanks. Allan Carson

 		 	   		  
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