Hello list members,
I'm trying to get nlme to work with lsoda from odesolve. Currently, I can use nlsList to fit a simple logistic growth model to some simulated data, but I get the following error message with nlme: "Error in model.frame(formula, rownames, variables, varnames, extras, extranames, : invalid variable type"
The commands I'm trying are below. Any suggestions for how to get this to work?
Thanks!
This works: fit.nlsList<-nlsList(xvals~lsoda(x0,times,Logist, +c(r=r,K=K,x0=x0))[,2]|group, +start=list(r=1,K=500,x0=2),data=data.group)
This returns the error message above: fit.nlme<-nlme(xvals~(lsoda(x0,times,Logist, +c(r=r,K=K,x0=x0))[,2]), +start=list(r=1,K=500,x0=2),data=data.group, +fixed=r+K+x0~1,random=x0~1)
The model function is:
Logist=function(t,x,parms) {
N1<-x[1]
with(as.list(parms),{
dN1=r*N1*(1-(N1/K))
list(c(dN1))
})}My data set looks like:
Grouped Data: xvals ~ times | group
xvals times group
1 -0.44543969 0 1
2 38.86411972 3 1
3 310.77106961 6 1
4 486.78653327 9 1
5 0.40613173 0 2
6 34.94635643 3 2
7 307.81884870 6 2
8 486.46098417 9 2
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