Hi! First I would like to thank you for the help with my first question. However,I am afraid I am still into trouble. I think I have properly used the getGropus commad but seems to be a fatal error when calculating the fixed effects (see bellow) and I cannot understand why. Any inputs? Thanks in advance, /Jose hongos1=read.table("c:/temp/hongos1.txt", header=T)> attach(hongos1) > Tra=factor(Tra) > Ind=factor(Ind) > Rep=factor(Rep) > names(hongos1)[1] "Esp" "Tra" "Ind" "Rep" "Are" "Cre"> hongos1$TraInd= getGroups(hongos1, form = ~1|Tra/Ind, level = 2) > model=lme(Cre~Tra,random=~1|Tra/Ind/Rep) > summary(model)Linear mixed-effects model fit by REML Data: NULL AIC BIC logLik 30.88467 41.5423 -7.442334 Random effects: Formula: ~1 | Tra (Intercept) StdDev: 0.07849531 Formula: ~1 | Ind %in% Tra (Intercept) StdDev: 0.1536001 Formula: ~1 | Rep %in% Ind %in% Tra (Intercept) Residual StdDev: 0.2242143 0.08325685 Fixed effects: Cre ~ Tra Error in if (any(wchLv <- (as.double(levels(xtTab[, wchPval])) == 0))) { : missing value where logical needed In addition: Warning message: NaNs produced in: pt(q, df, lower.tail, log.p) [[alternate HTML version deleted]]