This function is generic; method functions can be written to handle
  specific classes of objects. Classes which already have methods for
  this function include all "pdMat",
  "corStruct" and "varFunc" classes,
  "reStruct", and "modelStruct".
coefficients<- is an alias for coef<-.
coef(object, ...) <- valuecoefficients(object, ...) <- value
will depend on the method function; see the appropriate documentation.
any object representing a fitted model, or, by default,
   any object with a coef component.
some methods for this generic function may require additional arguments.
a value to be assigned to the coefficients associated with
   object.
José Pinheiro and Douglas Bates bates@stat.wisc.edu