5 research outputs found
Improving Neural Additive Models with Bayesian Principles
Neural additive models (NAMs) can improve the interpretability of deep neural
networks by handling input features in separate additive sub-networks. However,
they lack inherent mechanisms that provide calibrated uncertainties and enable
selection of relevant features and interactions. Approaching NAMs from a
Bayesian perspective, we enhance them in three primary ways, namely by a)
providing credible intervals for the individual additive sub-networks; b)
estimating the marginal likelihood to perform an implicit selection of features
via an empirical Bayes procedure; and c) enabling a ranking of feature pairs as
candidates for second-order interaction in fine-tuned models. In particular, we
develop Laplace-approximated NAMs (LA-NAMs), which show improved empirical
performance on tabular datasets and challenging real-world medical tasks
Delphic Offline Reinforcement Learning under Nonidentifiable Hidden Confounding
A prominent challenge of offline reinforcement learning (RL) is the issue of
hidden confounding: unobserved variables may influence both the actions taken
by the agent and the observed outcomes. Hidden confounding can compromise the
validity of any causal conclusion drawn from data and presents a major obstacle
to effective offline RL. In the present paper, we tackle the problem of hidden
confounding in the nonidentifiable setting. We propose a definition of
uncertainty due to hidden confounding bias, termed delphic uncertainty, which
uses variation over world models compatible with the observations, and
differentiate it from the well-known epistemic and aleatoric uncertainties. We
derive a practical method for estimating the three types of uncertainties, and
construct a pessimistic offline RL algorithm to account for them. Our method
does not assume identifiability of the unobserved confounders, and attempts to
reduce the amount of confounding bias. We demonstrate through extensive
experiments and ablations the efficacy of our approach on a sepsis management
benchmark, as well as on electronic health records. Our results suggest that
nonidentifiable hidden confounding bias can be mitigated to improve offline RL
solutions in practice
Neighborhood Contrastive Learning Applied to Online Patient Monitoring
Intensive care units (ICU) are increasingly looking towards machine learning for methods to provide online monitoring of critically ill patients. In machine learning, online monitoring is often formulated as a supervised learning problem. Recently, contrastive learning approaches have demonstrated promising improvements over competitive supervised benchmarks. These methods rely on well-understood data augmentation techniques developed for image data which do not apply to online monitoring. In this work, we overcome this limitation by supplementing time-series data augmentation techniques with a novel contrastive learning objective which we call neighborhood contrastive learning (NCL). Our objective explicitly groups together contiguous time segments from each patient while maintaining state-specific information. Our experiments demonstrate a marked improvement over existing work applying contrastive methods to medical time-series.ISSN:2640-349
Neighborhood Contrastive Learning Applied to Online Patient Monitoring
Intensive care units (ICU) are increasingly looking towards machine learning for methods to provide online monitoring of critically ill patients. In machine learning, online monitoring is often formulated as a supervised learning problem. Recently, contrastive learning approaches have demonstrated promising improvements over competitive supervised benchmarks. These methods rely on well-understood data augmentation techniques developed for image data which do not apply to online monitoring. In this work, we overcome this limitation by supplementing time-series data augmentation techniques with a novel contrastive learning objective which we call neighborhood contrastive learning (NCL). Our objective explicitly groups together contiguous time segments from each patient while maintaining state-specific information. Our experiments demonstrate a marked improvement over existing work applying contrastive methods to medical time-series.ISSN:2640-349