Adaptive exact recovery in sparse nonparametric models

TL;DR

This paper develops an adaptive method for exact variable selection in high-dimensional sparse nonparametric regression models observed in Gaussian white noise, addressing the challenges of increasing dimension and unknown sparsity.

Contribution

It introduces a new adaptive selection procedure that achieves exact recovery of nonzero components in high-dimensional nonparametric models with unknown sparsity.

Findings

Conditions for exact variable selection are derived.

The proposed procedure is adaptive to sparsity levels.

Conditions under which exact selection is impossible are identified.

Abstract

We observe an unknown regression function of $d$ variables $f(\boldsymbol{t})$, $\boldsymbol{t} \in[0,1]^d$, in the Gaussian white noise model of intensity $\varepsilon>0$. We assume that the function $f$ is regular and that it is a sum of $k$-variate functions, where $k$ varies from $1$ to $s$ ($1\leq s\leq d$). These functions are unknown to us and only few of them are nonzero. In this article, we address the problem of identifying the nonzero components of $f$ in the case when $d=d_\varepsilon\to \infty$ as $\varepsilon\to 0$ and $s$ is either fixed or $s=s_\varepsilon\to \infty$, $s=o(d)$ as $\varepsilon\to \infty$. This may be viewed as a variable selection problem. We derive the conditions when exact variable selection in the model at hand is possible and provide a selection procedure that achieves this type of selection. The procedure is adaptive to a degree of model sparsity described by the sparsity parameter $\beta\in(0,1)$. We also derive conditions that make the exact variable selection impossible. Our results augment previous work in this area.