[R] nlsList vs nlme with lsoda function

[Manuel Morales]

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
etc...