Ordinal Methods: Concepts, Applications, New Developments and Challenges

The year 2022 marks the 20th anniversary of the seminal paper of C. Bandt and B. Pompe on permutation entropy. During this time, the new "ordinal" methodology has been developed by theoreticians and practitioners in different directions. However, many of the new concepts and approaches are not fully understood and there is also a need for a more systematic application of ordinal methods. Precisely, this Focus Issue aims to be a forum where researchers from different disciplines can report on recent advances in ordinal methods, thus making further progress and synergies possible. We expect mostly original contributions but also some minireviews from different perspectives. In particular, manuscripts on statistical aspects of the ordinal patterns, ordinal methods in machine learning, and numerical benchmarking of ordinal methods in specific applications are especially welcome.

Guest Editors: José M. Amigó, Karsten Keller, Osvaldo A. Rosso