Re: Nugget effect

[Edzer J. Pebesma]

Don't interpret it. It's a consequence of the automatic
fitting routine. This routine only minimizes weighted sums
of squares, and does not pay attention to the fact that
a nugget is always a variance, and therefore is not allowed
to become negative.

The advice is to remove the nugget effect, or to fix it,
prior to fitting, at a positive value.
--
Edzer