Dear all,

I am running mixed effects models using the nlme package.  I am working
with a dataset where spatial autocorrelation is inherent in the response
variable.  I have tested each of the five correlation structures that are
available for mixed models in nlme, but none of these functions fit my
spatial correlation pattern very well.  To quote Pinheiro and Bates (2000),
"New corStruct classes, representing user-defined correlation structures,
can be added to the set of standard classes and used with the modeling
functions in the nlme library. For this, one must specify a constructor
function, generally with the same name as the class, and, at a minimum,
methods for the functions coef, corMatrix, and initialize."  I am fairly
new to R and could benefit from an example showing how this is done.  I've
spent a couple of days searching the net and haven't come up with
anything.  Can anyone refer me to a good source where a custom corStruct
class is created and run with gls or lme?

Thank you for your help,

-- 
Shawn O'Neil
Research Assistant, Applied Ecology
Forest Resources and Environmental Science
Michigan Technological University
701-741-4361

	[[alternative HTML version deleted]]

