Multiscale Change-point Segmentation: Beyond Step Functions

TL;DR

This paper extends multiscale change-point segmentation methods beyond step functions to more general function classes like bounded variation and Hölder functions, providing theoretical guarantees and demonstrating near-optimal performance.

Contribution

It introduces a universal thresholding approach for multiscale segmentation applicable to broader function classes, enhancing robustness and theoretical understanding.

Findings

Methods are robust to deviations from step functions.

Performance is nearly optimal compared to oracle estimators.

Theoretical guarantees are supported by numerical simulations.

Abstract

Modern multiscale type segmentation methods are known to detect multiple change-points with high statistical accuracy, while allowing for fast computation. Underpinning theory has been developed mainly for models that assume the signal as a piecewise constant function. In this paper this will be extended to certain function classes beyond such step functions in a nonparametric regression setting, revealing certain multiscale segmentation methods as robust to deviation from such piecewise constant functions. Our main finding is the adaptation over such function classes for a universal thresholding, which includes bounded variation functions, and (piecewise) H\"{o}lder functions of smoothness order $ 0 < \alpha \le1$ as special cases. From this we derive statistical guarantees on feature detection in terms of jumps and modes. Another key finding is that these multiscale segmentation methods perform nearly (up to a log-factor) as well as the oracle piecewise constant segmentation estimator (with known jump locations), and the best piecewise constant approximants of the (unknown) true signal. Theoretical findings are examined by various numerical simulations.