Lookup NU author(s): Dr Alfredo Alegria Jimenez,
Professor Emilio Porcu
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© 2017 Informa UK Limited, trading as Taylor & Francis Group Matrix-valued covariance functions are crucial to geostatistical modelling of multivariate spatial data. The classical assumption of symmetry of a multivariate covariance function is overly restrictive and has been considered as unrealistic for most of the real data applications. Despite of that, the literature on asymmetric covariance functions has been very sparse. In particular, there is some work related to asymmetric covariances on Euclidean spaces, depending on the Euclidean distance. However, for data collected over large portions of planet Earth, the most natural spatial domain is a sphere, with the corresponding geodesic distance being the natural metric. In this work, we propose a strategy based on spatial rotations to generate asymmetric covariances for multivariate random fields on the d-dimensional unit sphere. We illustrate through simulations as well as real data analysis that our proposal allows to achieve improvements in the predictive performance in comparison to the symmetric counterpart.
Author(s): Alegria A, Porcu E, Furrer R
Publication type: Article
Publication status: Published
Journal: Journal of Statistical Computation and Simulation
Online publication date: 27/11/2017
Acceptance date: 14/11/2017
ISSN (print): 0094-9655
ISSN (electronic): 1563-5163
Publisher: Taylor and Francis Ltd
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