Re: [R] Using NLS with a Kappa function

Actually it just the parameterization that is causing trouble near k=0 let u = (x-z)/a then the problematic part of your function is (1- k*u)^(1/k) take the log to get log(1-k*u)/k = -(k*u +k^2*u^2/2 + ...)/k = -(u +k u^2/2 + ..) so your function is exp(-u - ku^2/2 - ...) and u

Re: [R] Using NLS with a Kappa function

Hi Ezra, I'm not any sort of expert on this but my own attempts to get nls to fit functions similar in form to your kappa equation have usually provoked the same error messages. It might be worth log transforming your dependent variable and trying to fit this: -log(h) * ( -log(k) * log(1 - h *

[R] Using NLS with a Kappa function

Hi Everyone, I am trying to use NLS to fit a dataset using a Kappa function, but I am having problems. Depending on the start values that I provide, I get either: Error in numericDeriv(form[[3L]], names(ind), env) : Missing value or an infinity produced when evaluating the model Or Error in nl