about
I'm an ELLIS PhD student at IST Austria supervised by Francesco Locatello, co-supervised by Arthur Gretton at the Gatsby Computational Neuroscience Unit, University College London.
My recent work focuses on the identifiability of representations in modern machine learning models, particularly foundation-scale models. I'm motivated by problems in biology that offer the chance to gain insights into the mechanisms of human disease and behaviour, and in medicine with the potential for real-world impact on patient care.
Previously, I was a full-time staff data scientist at the Centre for Data Science and Digital Health (CREATE) at Hamilton Health Sciences in Hamilton, Canada. During my undergraduate studies, I worked in the lab of Anna Goldenberg at The Hospital for Sick Children in Toronto. In the past, I've also consulted on software engineering, machine learning engineering, and data science projects ranging from back office finance to consumer-facing mobile and web applications.
[github] [scholar] [linkedin]employment
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Research Consultant
Chan Zuckerberg Initiative Foundation
March 2025 - June 2025 -
Junior Data Scientist
Centre for Data Science & Digital Health, Hamilton Health Sciences
2019 - 2024
education
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Doctor of Philosophy, Computer Science
Institute of Science and Technology Austria
2024 - present -
Master of Science, Statistics
University of Toronto
2021 - 2024 -
Honours Bachelor of Science, Bioinformatics and
Computational Biology & Neuroscience
University of Toronto
2015 - 2019
selected publications
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Statistical and structural identifiability in representation learning
ICLR, 2026 [arxiv]
Walter Nelson, Marco Fumero, Theofanis Karaletsos, Francesco Locatello -
Detecting irregularities in randomized controlled trials using machine learning
Clinical Trials, 2024 [doi]
Walter Nelson*, Jeremy Petch*, Jonathan Ranisau, Robin Zhao, Kumar Balasubramanian, Shrikant Bangdiwala -
Optimizing warfarin dosing for patients with atrial fibrillation using machine learning
Scientific Reports, 2024 [doi]
Jeremy Petch, Walter Nelson, Mary Wu, Marzyeh Ghassemi, Alexander Benz, Mehdi Fatemi, Shuang Di, Anthony Carnicelli, Christopher Granger, Robert Giugliano, Hwanhee Hong, Manesh Patel, Lars Wallentin, John Eikelboom, Stuart Connolly
open source & side projects
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SanteMPI Record Linkage Configuration Optimizer
Through our work at CREATE, I engineered a plugin for optimizing the parameters of the SanteMPI patient record linkage algorithm using Bayesian optimization. Sante software underpins national deployments in Tanzania and Myanmar. -
Compare Concordance
I authored a Python port of the compareC R library for doing statistical inference about correlated right-censored c-indices, which commonly arise in the comparison of predictive survival models. The package is available on PyPi.