Modelling spatio-temporal data: A new variogram and covariance structure proposal

We adapt the Dagum survival function to become a function of space and time and study its theoretical properties as a covariance in the isotropic case. The resulting Dagum class is proved to have certain interesting mathematical properties and shows smooth behaviour at the origin, which has considerable applicability. A simple extension to the spatio-temporal case is provided and interesting points of comparison arise with other models appearing in literature.