Abstract:
We consider the following sparse signal recovery (or feature selection) problem: given a design matrix X∈Rn×m (m≫n) and a noisy observation vector y∈Rn satisfying y=Xβ∗+ϵ where ϵ is the noise vector following a Gaussian distribution N(0,σ2I), how to recover the signal (or parameter vector) β∗ when the signal
is sparse?
The Dantzig selector has been proposed for sparse signal recovery with strong theoretical guarantees. In this paper, we propose a multi-stage Dantzig selector method, which iteratively refines the target signal β∗. We show that if X obeys a certain condition, then with a large probability the difference between the solution ˆβ estimated by the proposed method and the true
solution β∗ measured in terms of the lp norm (p≥1) is bounded as ‖ˆβ−β∗‖p≤(C(s−N)1/p√logm+Δ)σ, C is a constant, s is the number of nonzero entries in β∗, Δ is independent of m and is much smaller than the first term, and N is the number of entries of β∗ larger
than a certain value in the order of O(σ√logm). The proposed method improves the estimation bound of the standard Dantzig selector approximately from Cs1/p√logmσ to C(s−N)1/p√logmσ where the value N
depends on the number of large entries in β∗. When N=s, the proposed algorithm achieves the oracle solution with a high probability. In addition, with a large probability, the proposed method can select the same number of correct features under a milder condition than the Dantzig selector.
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