Hi, I have R 2.6.0 with updated lme4 and Matrix packages, and I am trying to fit a nonlinear multilevel model. I get the following error message:
Error in nlmer(f ~ grModel(x, w, Tmin, Tmax, Topt, kopt, m) ~ kopt | flat, : gradient attribute of evaluated model must be a numeric matrix and I wonder what this may indicate. The nonlinear model I try to fit is as follows: > grModel function(x,w,Tmin,Tmax,Topt,kopt,m)((x-Tmin)*(x-Tmax))/((x-Tmin)*(x-Tmax)-(x-Topt)^2)*kopt*w^m and my call of nlmer is as follows: nlmr1<-nlmer(feed~grModel(temp,MW,Tmin,Tmax,Topt,kopt,m)~kopt| flat,data=egi,start=c(Tmin=0.2,Tmax=21.1,Topt=14.6,kopt=2.5,m=.51)) 'flat' is a factor with 11 levels. My start values are from nls that fits the model with no errors. The call I have used is as follows: nls1<-nls(feed~grModel(temp,MW,Tmin,Tmax,Topt,kopt,m),data=egi,start=c(Tmin=1,Tmax=20,Topt=13,kopt=3,m=.7)) The examples given on the help page of nlmer run with no errors. I would appreciate any hints and help to track the problem indicated by the error message. Thanks, Kari ______________________________________________ R-help@r-project.org 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.
