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.