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...

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