Selecting the number of states in Hidden Markov Models:Pragmatic solutions illustrated using animal movement

We discuss the notorious problem of order selection in hidden Markov models, that is of selecting an adequate number of states, highlighting typical pitfalls and practical challenges arising when analyzing real data. Extensive simulations are used to demonstrate the reasons that render order selecti...

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Bibliographic Details
Published in:Journal of Agricultural, Biological and Environmental Statistics
Main Authors: Langrock, Roland, Pohle, Jennifer, van Beest, Floris, Schmidt, Niels Martin
Format: Article in Journal/Newspaper
Language:English
Published: 2017
Subjects:
Online Access:https://pure.au.dk/portal/en/publications/0a38b759-c71a-4c3e-926d-14cf9f690d19
https://doi.org/10.1007/s13253-017-0283-8
Description
Summary:We discuss the notorious problem of order selection in hidden Markov models, that is of selecting an adequate number of states, highlighting typical pitfalls and practical challenges arising when analyzing real data. Extensive simulations are used to demonstrate the reasons that render order selection particularly challenging in practice despite the conceptual simplicity of the task. In particular, we demonstrate why well-established formal procedures for model selection, such as those based on standard information criteria, tend to favor models with numbers of states that are undesirably large in situations where states shall be meaningful entities. We also offer a pragmatic step-by-step approach together with comprehensive advice for how practitioners can implement order selection. Our proposed strategy is illustrated with a real-data case study on muskox movement. Supplementary materials accompanying this paper appear online.