Abstract
Given a set of vectors (the data) in a Hilbert space ℋ, we prove the existence of an optimal collection of subspaces minimizing the sum of the square of the distances between each vector and its closest subspace in the collection. This collection of subspaces gives the best sparse representation for the given data, in a sense defined in the paper, and provides an optimal model for sampling in union of subspaces. The results are proved in a general setting and then applied to the case of low dimensional subspaces of ℝN and to infinite dimensional shift-invariant spaces in L 2(ℝd). We also present an iterative search algorithm for finding the solution subspaces. These results are tightly connected to the new emergent theories of compressed sensing and dictionary design, signal models for signals with finite rate of innovation, and the subspace segmentation problem.
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Communicated by Michael Elad.
The research of Akram Aldroubi is supported in part by NSF Grant DMS-0504788. The research of Carlos Cabrelli and Ursula Molter is partially supported by Grants: PICT 15033, CONICET, PIP 5650, UBACyT X058 and X108.
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Aldroubi, A., Cabrelli, C. & Molter, U. Optimal Non-Linear Models for Sparsity and Sampling. J Fourier Anal Appl 14, 793–812 (2008). https://doi.org/10.1007/s00041-008-9040-2
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DOI: https://doi.org/10.1007/s00041-008-9040-2