help with nls and Hill equation
I think its your parameterization that is problematic. ED50^hill is tough for it to work with since both are varying. Try reparameterizing using ED50hill = ED50^hill as a parameter so that the parameters become Emax, ED50hill and hill. You can back transform afterwards.
On 10/16/07, Lanre Okusanya <lanre.okusanya at gmail.com> wrote:
Hello all, I am having a problem with nls. I have such data as shown below, foo<- Dose var 0 0.000000 100 -1.318178 200 -1.562425 400 -3.579960 1200 -3.788662 however, when I call nls as shown below,
foo.nls<-nls(var~Emax*(Dose^hill)/((EC50^hill)+(Dose^hill)),
+ start=list(Emax=-4,EC50=269,hill=1),trace=T,data=foo)
i get the response below.
1.759088 : -4 269 1
Error in numericDeriv(form[[3]], names(ind), env) :
Missing value or an infinity produced when evaluating the model
if i remove the hill variable, it works. can someone help me out with
what I am coding wrong.
Thanks,
Lanre
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