Tropical Logistic Regression Model on Space of Phylogenetic Trees

Aliatimis, George and Yoshida, Ruriko and Boyacı, Burak and Grant, James (2024) Tropical Logistic Regression Model on Space of Phylogenetic Trees. Bulletin of Mathematical Biology, 86: 99. ISSN 0092-8240

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Abstract

Classification of gene trees is an important task both in the analysis of multi-locus phylogenetic data, and assessment of the convergence of Markov Chain Monte Carlo (MCMC) analyses used in Bayesian phylo- genetic tree reconstruction. The logistic regression model is one of the most popular classification models in statistical learning, thanks to its computational speed and interpretability. However, it is not appropriate to directly apply the standard logistic regression model to a set of phylo- genetic trees, as the space of phylogenetic trees is non-Euclidean and thus contradicts the standard assumptions on covariates. It is well-known in tropical geometry and phylogenetics that the space of phylogenetic trees is a tropical linear space in terms of the max-plus algebra. Therefore, in this paper, we propose an analogue approach of the logistic regression model in the setting of tropical geometry. Our proposed method outperforms classical logistic regression in terms of Area under the ROC Curve (AUC) in numerical examples, including with data generated by the multi-species coalescent model. Theoretical properties such as statistical consistency have been proved and general- ization error rates have been derived. Finally, our classification algorithm is proposed as an MCMC convergence criterion for Mr Bayes. Unlike the convergence metric used by Mr Bayes which is only dependent on tree topologies, our method is sensitive to branch lengths and therefore pro- vides a more robust metric for convergence. In a test case, it is illustrated that the tropical logistic regression can differentiate between two indepen- dently run MCMC chains, even when the standard metric cannot.