Hello, I was following the sample in the grass book and I'm getting a error message using gstat.cv. message is: > pe1 <- gstat.cv(t2, debug.leve=0, random=FALSE)$residual Error in unique(fold) : object 'fold' not found I appreciate if anyone could show me where is the error. thanks. -- http://www.monsterhuntercommunity.com/license/nynxs