Re: [R] Non-constant variance and non-Gaussian errors with gnls

Well, it looks like I am partly answering my own question. gnls is clearly not going to be the right method to use to try out a non-Gaussian error structure. The "ls"=Least Squares in "gnls" means minimising the sum of the square of the residuals ... which is equivalent to assuming a Gaussian error

[R] Non-constant variance and non-Gaussian errors with gnls

I have been using the nls function to fit some simple non-linear regression models for properties of graphite bricks to historical datasets. I have then been using these fits to obtain mean predictions for the properties of the bricks a short time into the future. I have also been calculating appro