Spiked Laplacian Graphs: Bayesian Community Detection in Heterogeneous Networks

TL;DR

This paper introduces a Bayesian probabilistic model for community detection in heterogeneous networks, enabling uncertainty quantification and improved analysis of multiple related graphs.

Contribution

It proposes the Spiked Laplacian Graph model and a Bayesian non-parametric approach to handle heterogeneity, with theoretical guarantees and practical applications.

Findings

Model achieves accurate community detection in synthetic data

Provides uncertainty measures for community assignments

Demonstrates effectiveness on neuroscience data

Abstract

In network data analysis, it is becoming common to work with a collection of graphs that exhibit \emph{heterogeneity}. For example, neuroimaging data from patient cohorts are increasingly available. A critical analytical task is to identify communities, and graph Laplacian-based methods are routinely used. However, these methods are currently limited to a single network and do not provide measures of uncertainty on the community assignment. In this work, we propose a probabilistic network model called the ``Spiked Laplacian Graph'' that considers each network as an invertible transform of the Laplacian, with its eigenvalues modeled by a modified spiked structure. This effectively reduces the number of parameters in the eigenvectors, and their sign patterns allow efficient estimation of the community structure. Further, the posterior distribution of the eigenvectors provides uncertainty quantification for the community estimates. Subsequently, we introduce a Bayesian non-parametric approach to address the issue of heterogeneity in a collection of graphs. Theoretical results are established on the posterior consistency of the procedure and provide insights on the trade-off between model resolution and accuracy. We illustrate the performance of the methodology on synthetic data sets, as well as a neuroscience study related to brain activity in working memory. Keywords: Hierarchical Community Detection, Isoperimetric Constant, Mixed-Effect Eigendecomposition, Normalized Graph Cut, Stiefel Manifold