[R] Re: creating new varFunc classes in nlme .. error: "Don't know how to get coefficients for .. object"

[Prof Brian Ripley]

On Sun, 3 Oct 2004, J wrote:

> Ah!! After way too many hours of work Ive answered my
> own question.  To get varExp2, a copy of varExp, to
> work as a new varFunc, one needs to use this sort of
> syntax:
> 
> update.varExp2 <- function (object, data, ...)
> {
>     print ("enter update")
>     val <- NextMethod()
>     if (length(val) == 0) {
>         aux <- coef(val, allCoef = TRUE)
>         if (!is.null(grps <- getGroups(val))) {
>             aux <- aux[grps]
>         }
>         attr(val, "logLik") <- sum(log(attr(val,
> "weights") <- exp(-aux *
>             getCovariate(val))))
>     }
>     val
> }
> setMethod("update", "varExp2", update.varExp2)

update() is an S3 generic and nlme uses S3 classes, so this is definitely 
wrong.  Have you been using S4 classes without mentioning it?

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595