Nonlinear Approximation with Walsh Atoms
نویسندگان
چکیده
As a model for nonlinear approximation from a redundant set of time-frequency atoms, we consider approximation in L 2 (IR) with linear combinations of Walsh at oms. Best approximation can be realized with a fast algorithm when the class of approximants is restricted to linear combinations of pairwise orthogonal atoms. We describe the eeect of this restriction on approximation rates, and then discuss the performance of the greedy algorithm. In particular, a uniform geometric rate of convergence is shown to hold for the class of initial functions consisting of linear combinations of two atoms.
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