Don't Explain Noise: Robust Counterfactuals for Randomized Ensembles

Fuente: arXiv
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Main Authors: Forel, Alexandre, Parmentier, Axel, Vidal, Thibaut
Format: Preprint
Published: 2022
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author Forel, Alexandre
Parmentier, Axel
Vidal, Thibaut
author_facet Forel, Alexandre
Parmentier, Axel
Vidal, Thibaut
contents Counterfactual explanations describe how to modify a feature vector in order to flip the outcome of a trained classifier. Obtaining robust counterfactual explanations is essential to provide valid algorithmic recourse and meaningful explanations. We study the robustness of explanations of randomized ensembles, which are always subject to algorithmic uncertainty even when the training data is fixed. We formalize the generation of robust counterfactual explanations as a probabilistic problem and show the link between the robustness of ensemble models and the robustness of base learners. We develop a practical method with good empirical performance and support it with theoretical guarantees for ensembles of convex base learners. Our results show that existing methods give surprisingly low robustness: the validity of naive counterfactuals is below $50\%$ on most data sets and can fall to $20\%$ on problems with many features. In contrast, our method achieves high robustness with only a small increase in the distance from counterfactual explanations to their initial observations.
format Preprint
id arxiv_https___arxiv_org_abs_2205_14116
institution arXiv
publishDate 2022
record_format arxiv
spellingShingle Don't Explain Noise: Robust Counterfactuals for Randomized Ensembles
Forel, Alexandre
Parmentier, Axel
Vidal, Thibaut
Machine Learning
Optimization and Control
Counterfactual explanations describe how to modify a feature vector in order to flip the outcome of a trained classifier. Obtaining robust counterfactual explanations is essential to provide valid algorithmic recourse and meaningful explanations. We study the robustness of explanations of randomized ensembles, which are always subject to algorithmic uncertainty even when the training data is fixed. We formalize the generation of robust counterfactual explanations as a probabilistic problem and show the link between the robustness of ensemble models and the robustness of base learners. We develop a practical method with good empirical performance and support it with theoretical guarantees for ensembles of convex base learners. Our results show that existing methods give surprisingly low robustness: the validity of naive counterfactuals is below $50\%$ on most data sets and can fall to $20\%$ on problems with many features. In contrast, our method achieves high robustness with only a small increase in the distance from counterfactual explanations to their initial observations.
title Don't Explain Noise: Robust Counterfactuals for Randomized Ensembles
topic Machine Learning
Optimization and Control
url https://arxiv.org/abs/2205.14116