Isotropic processes form an inadequate basis in modelling many spatially distributed data. In particular environmental phenomena often have strong anisotropic spatial variation, especially when the regions monitored are very large. We extend a recently proposed optimal sampling strategy by...

The design of a stratified sample from a finite population deals with two main issues: the definition of a rule to partition the population, and the allocation of sampling units in the selected strata. This article examines a tree-based strategy which plans to solve jointly these issues when the...

The concept of convergence clubs is analyzed and compared with classical methods for the study of economic [beta]-convergence, which often consider the entire data set as one sample. A technique for the identification of convergence clubs is proposed. The algorithm is based on a modified version...