Could somebody help with the definition of new correlation structure for use with a linear mixed-effects model (package nlme). Specifically, I want to define a Toeplitz type correlation structure, but due to my inexperience with programming in R, I feel a bit overwhelmed with the task at hand.
I understand that you can start with a function like corAR1 as template, but I have no idea how I would define the methods (coef, corMatrix, and initialize) in this context.
I did a search on Google and in the R-help archives, but have not found much in terms of hints and specific examples for user defined correlation structures.
Thank you in advance!
Michael Jerosch-Herold