Using this parametrization for a growth curve logistic model
I created some points with: K =0.7 ; y0=0.01 ; r =0.3
df = data.frame(x= seq(1, 50, by = 5))
df$y = 0.7/(1+((0.7-0.01)/0.01)*exp(-0.3*df$x))
Can someone tell me how can I have a fitting error if create the data with the model starters?
fo = df$y ~ K/(1+((K-y0)/y0)*exp(-r*df$x))
model<-nls(fo,
start = list(K=0.7, y0=0.01, r=0.3),
df,
nls.control(maxiter = 1000))
Error in nls(fo, start = list(K = 0.7, y0 = 0.01, r = 0.3), df, nls.control(maxiter = 1000)) :
number of iterations exceeded maximum of 1000
Do not use ‘nls’ on artificial "zero-residual" data., as documented in
?nls
.Also, avoid using
$
in model formula, otherwise you will get into trouble when usingpredict
later.