nls200<-nlsList(prop~select_fun(q1,q2,a,b,p,Length),start=start_vec,
               data=new.data_200,control=nls.control(maxiter=500,tol=1e-4,minFactor=1/5000,
               printEval=T))

select_fun<-function(q1,q2,a,b,p,Length){
                   expo=exp(a+b*Length)
                   r=expo/(1+expo)
                   phi=q1*p*r/(q1*p*r+q2*(1-p))
    }

nls200.2<-nlme(nls200,random=p~1,control=nlmeControl(maxIter=50,
               minScale=0.001,tolerance=1e-5,niterEM=25,msVerbose=T))

xyplot(residuals(mc1) ~ fitted(mc1) | new.data_200.2$StationID,layout=c(5,5),
  panel=function(x, y){
    panel.xyplot(x, y)
    try(panel.loess(x, y) )
  }
)