Nonparametric Functional Graphical Modeling Through Functional Additive Regression Operator

Kuang‐Yao Lee

doi:10.1080/01621459.2021.2006667

Nonparametric Functional Graphical Modeling Through Functional Additive Regression Operator

2022-01-05

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DOI：10.1080/01621459.2021.2006667

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In this article, we develop a nonparametric graphical model for multivariate random functions. Most existing graphical models are restricted by the assumptions of multivariate Gaussian or copula Gaussian distributions, which also imply linear relations among the random variables or functions on different nodes. We relax those assumptions by building our graphical model based on a new statistical object-the functional additive regression operator. By carrying out regression and neighborhood selection at the operator level, our method can capture nonlinear relations without requiring any distributional assumptions. Moreover, the method is built up using only one-dimensional kernel, thus, avoids the curse of dimensionality from which a fully nonparametric approach often suffers, and enables us to work with large-scale networks. We derive error bounds for the estimated regression operator and establish graph estimation consistency, while allowing the number of functions to diverge at the exponential rate of the sample size. We demonstrate the efficacy of our method by both simulations and analysis of an electroencephalography dataset. Supplementary materials for this article are available online.

Keywords:

Additive conditional independence

Brain connectivity analysis

Graphical model

Neuroimaging analysis

Regression operator

Sparsistency

Nonparametric Functional Graphical Modeling Through Functional Additive Regression Operator

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