The H-IAR Model for Irregular Multispectral Time Series. Quaternion Formulation, Mapping of Resilience Indicators, and Exploratory Identification of Forest Edges

We propose the Hypercomplex Irregular Autoregressive (\HIAR) model, a quaternion extension of the \IAR/\CIAR/\BIAR{} family for four-component observations at irregular times. Temporal dependence is represented by a real power of a quaternion parameter and estimated in state-space form through the G