Coba jelasin Model Variogram dari Variogram dalam bahasa sunda dong

The empirical variogram cannot be computed at every lag distance  and due to variation in the estimation it is not ensured that it is a valid variogram, as defined above. However some Geostatistical methods such as kriging need valid semivariograms. In applied géostatistics the empirical variograms are thus often approximated by modél function ensuring validity (Chiles&Delfiner 1999). Some important modéls are (Chiles&Delfiner 1999, Cressie 1993):