Structure and Stability of the 1-Dimensional Mapper

TL;DR

This paper develops a theoretical framework to understand the structure and stability of the 1-dimensional Mapper, relating it to the Reeb graph and providing guarantees on its features and convergence.

Contribution

It introduces a framework linking Mapper's structure to the Reeb graph, enabling prediction of features and stability analysis based on function and cover positioning.

Findings

Predicts Mapper features based on cover placement

Quantifies stability of Mapper features

Provides convergence guarantees to Reeb graph

Abstract

Given a continuous function $f:X\to\mathbb{R}$ and a cover $\mathcal{I}$ of its image by intervals, the Mapper is the nerve of a refinement of the pullback cover $f^{-1}(\mathcal{I})$. Despite its success in applications, little is known about the structure and stability of this construction from a theoretical point of view. As a pixelized version of the Reeb graph of $f$, it is expected to capture a subset of its features (branches, holes), depending on how the interval cover is positioned with respect to the critical values of the function. Its stability should also depend on this positioning. We propose a theoretical framework that relates the structure of the Mapper to the one of the Reeb graph, making it possible to predict which features will be present and which will be absent in the Mapper given the function and the cover, and for each feature, to quantify its degree of (in-)stability. Using this framework, we can derive guarantees on the structure of the Mapper, on its stability, and on its convergence to the Reeb graph as the granularity of the cover $\mathcal{I}$ goes to zero.