Breaking the Bandwidth Barrier: Geometrical Adaptive Entropy Estimation
This work addresses a fundamental challenge in data science for applications relying on information-theoretic measures, offering incremental improvements over existing methods.
The paper tackles the problem of estimating entropy and mutual information by combining geometric and kernel-based approaches, resulting in new estimators that outperform state-of-the-art methods with improved practical performance through local bandwidth choices and bias correction.
Estimators of information theoretic measures such as entropy and mutual information are a basic workhorse for many downstream applications in modern data science. State of the art approaches have been either geometric (nearest neighbor (NN) based) or kernel based (with a globally chosen bandwidth). In this paper, we combine both these approaches to design new estimators of entropy and mutual information that outperform state of the art methods. Our estimator uses local bandwidth choices of $k$-NN distances with a finite $k$, independent of the sample size. Such a local and data dependent choice improves performance in practice, but the bandwidth is vanishing at a fast rate, leading to a non-vanishing bias. We show that the asymptotic bias of the proposed estimator is universal; it is independent of the underlying distribution. Hence, it can be pre-computed and subtracted from the estimate. As a byproduct, we obtain a unified way of obtaining both kernel and NN estimators. The corresponding theoretical contribution relating the asymptotic geometry of nearest neighbors to order statistics is of independent mathematical interest.