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Interpolating and translation-invariant approximations of parametric dictionaries

Frédéric Champagnat 1 Cédric Herzet 2
2 SIMSMART - SIMulation pARTiculaire de Modèles Stochastiques
IRMAR - Institut de Recherche Mathématique de Rennes, Inria Rennes – Bretagne Atlantique
Abstract : In this paper, we address the problem of approximating the atoms of a parametric dictionary A = {a(θ) : θ ∈ Θ}, commonly encountered in the context of sparse representations in "continuous" dictionaries. We focus on the case of translation-invariant dictionaries, where the inner product between a(θ) and a(θ) only depends on the difference θ − θ. We investigate the following general question: is there some low-rank approximation of A which interpolates a subset of atoms {a(θj)} J j=1 while preserving the translation-invariant nature of the original dictionary? In this paper, we derive necessary and sufficient conditions characterizing the existence of such an "interpolating" and "translation-invariant" low-rank approximation. Moreover, we provide closed-form expressions of such a dictionary when it exists. We illustrate the applicability of our results in the case of a two-dimensional isotropic Gaussian dictionary. We show that, in this particular setup, the proposed approximation framework outperforms standard Taylor approximation.
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Contributor : Cédric Herzet <>
Submitted on : Tuesday, December 15, 2020 - 6:24:03 PM
Last modification on : Friday, January 8, 2021 - 3:43:05 AM


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  • HAL Id : hal-03070383, version 1


Frédéric Champagnat, Cédric Herzet. Interpolating and translation-invariant approximations of parametric dictionaries. 28th European Signal Processing Conference (EUSIPCO 2020), Dec 2021, Amsterdam, Netherlands. ⟨hal-03070383⟩



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