[R] help with nls and Hill equation

[Lanre Okusanya]

Thanks.
I am just not used to having such a huge difference when changing the
initial condition by 1 point. it usually tends to be an issue when you
are way off (especially since the hill converged at 1.69). Does it
have something to do with the algorithm or is the hill just very
finicky?

Lanre


On 10/16/07, Christian Ritz <ritz at life.ku.dk> wrote:
> Hi!
>
> I would suggest trying out a few different starting values as a first unsystematic approach.
>
> For example changing hill=1 to hill=2 results in convergence:
>
> foo.nls<-nls(var~Emax*(Dose^hill)/((EC50^hill)+(Dose^hill)),
> start=list(Emax=-4,EC50=269,hill=2),trace=T,data=foo)
>
>
>
> Christian
>
>