Hello,
How do I specify the formula and random effects without a startup object ? I thought it would be a mixture of nls and lme. after trying very hard, I ask for help on using nlme. Can someone hint me to some examples? I constructed a try using the example from nls: #variables are density, conc and Run #all works fine with nls DNase1 <- subset(DNase, Run == 1 ) fm2DNase1 <- nls( density ~ 1/(1 + exp((xmid - log(conc))/scal)), data = DNase1, start = list(xmid = 0, scal = 1), trace = TRUE) #Now I want to do a mixed model with covariate Run #how is the syntax? DNase12 <- subset(DNase, Run == 1 | Run == 2) fm2DNase1 <- nlme( density ~ 1/(1 + exp((xmid - log(conc))/scal)), data = DNase12, fixed = conc ~ 1, random = Run ~ 1, start = list(xmid = 0, scal = 1) ) #gives: Error in eval(expr, envir, enclos) : object "xmid" not found Thomas ______________________________________________ R-help@stat.math.ethz.ch 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.