Re: [R] Assessing the fit of a nonlinear model to a new dataset

2013-04-12 Thread Rebecca Lester
Thank you all for your useful suggestions. Jean, I had already tried to use the maxiter command in that way, but it simply told me that the model had not converged. Based on Profs Ripley and Nash's comments, I have opted to use an alternative approach, and am creating a distribution of

[R] Assessing the fit of a nonlinear model to a new dataset

2013-04-05 Thread Rebecca Lester
Hi all, I am attempting to apply a nonlinear model developed using nls to a new dataset and assess the fit of that model. At the moment, I am using the fitted model from my fit dataset as the starting point for an nls fit for my test dataset (see below). I would like to be able to view the

Re: [R] Assessing the fit of a nonlinear model to a new dataset

2013-04-05 Thread Adams, Jean
Rebecca, I'm not sure why you are interested in the t-statistics and p-values for the iterations, but you could perhaps save the nls() fit after 1, 2, 3, ... iterations using the argument nls.control(maxiter = n). Jean On Fri, Apr 5, 2013 at 12:06 AM, Rebecca Lester

Re: [R] Assessing the fit of a nonlinear model to a new dataset

2013-04-05 Thread Prof Brian Ripley
On 05/04/2013 14:26, Adams, Jean wrote: Rebecca, I'm not sure why you are interested in the t-statistics and p-values for the iterations, but you could perhaps save the nls() fit after 1, 2, 3, ... iterations using the argument nls.control(maxiter = n). But those statistics are only even

Re: [R] Assessing the fit of a nonlinear model to a new dataset

2013-04-05 Thread Prof J C Nash (U30A)
Given nls has a lot of C code (and is pretty complicated), I doubt you'll find much joy doing that. nlxb from my nlmrt package is all in R, but you'll need to do quite a bit of work at each stage. I don't form the J' J matrix, and do a Marquardt approximation by adding appropriate rows to the