The two filter formula reconsidered: Smoothing in partially observed Gauss--Markov models without information parametrization

Fuente: arXiv
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Autor principal: Tronarp, Filip
Formato: Preprint
Publicado: 2025
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author Tronarp, Filip
author_facet Tronarp, Filip
contents In this article, the two filter formula is re-examined in the setting of partially observed Gauss--Markov models. It is traditionally formulated as a filter running backward in time, where the Gaussian density is parametrized in ``information form''. However, the quantity in the backward recursion is strictly speaking not a distribution, but a likelihood. Taking this observation seriously, a recursion over log-quadratic likelihoods is formulated instead, which obviates the need for ``information'' parametrization. In particular, it greatly simplifies the square-root formulation of the algorithm. Furthermore, formulae are given for producing the forward Markov representation of the a posteriori distribution over paths from the proposed likelihood representation.
format Preprint
id arxiv_https___arxiv_org_abs_2502_21116
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The two filter formula reconsidered: Smoothing in partially observed Gauss--Markov models without information parametrization
Tronarp, Filip
Methodology
Machine Learning
In this article, the two filter formula is re-examined in the setting of partially observed Gauss--Markov models. It is traditionally formulated as a filter running backward in time, where the Gaussian density is parametrized in ``information form''. However, the quantity in the backward recursion is strictly speaking not a distribution, but a likelihood. Taking this observation seriously, a recursion over log-quadratic likelihoods is formulated instead, which obviates the need for ``information'' parametrization. In particular, it greatly simplifies the square-root formulation of the algorithm. Furthermore, formulae are given for producing the forward Markov representation of the a posteriori distribution over paths from the proposed likelihood representation.
title The two filter formula reconsidered: Smoothing in partially observed Gauss--Markov models without information parametrization
topic Methodology
Machine Learning
url https://arxiv.org/abs/2502.21116