options(digits = 4)
set.seed(1131)
d = data.frame(x=runif(50),y=runif(50),z=runif(50),v=rnorm(50))
library(gstat)
xx = krige.cv(v~1,~x+y+z,d,model=vgm(1,"Exp",1), verbose=F, set=list(debug=0))
summary(xx)