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Considerable eeort has been directed recently to develop asymptotically mini-max methods in problems of recovering innnite-dimensional objects (curves, densities , spectral densities, images) from noisy data. A rich and complex body of work has evolved, with nearly-or exactly-minimax estimators being obtained for a variety of interesting problems.… (More)

Density estimation is a commonly used test case for non-parametric estimation methods. We explore the asymptotic properties of estimators based on thresholding of empirical wavelet coeecients. Minimax rates of convergence are studied over a large range of Besov function classes B s;p;q and for a range of global L 0 p error measures, 1 p 0 < 1. A single… (More)

- Wolfgang Härdle, Gerard Kerkyacharian, Dominique Picard, Alexander Tsybakov
- 2001

Deconvolution problems are naturally represented in the Fourier domain, whereas thresholding in wavelet bases is known to have broad adaptivity properties. We study a method which combines both fast Fourier and fast wavelet transforms and can recover a blurred function observed in white noise with O{n log.n/ 2 } steps. In the periodic setting, the method… (More)

We consider a sequence space model of statistical linear inverse problems where we need to estimate a function f from indirect noisy observations. Let a nite set of linear estimators be given. Our aim is to mimic the estimator in that has the smallest risk on the true f. Under general conditions, we show that this can be achieved by simple minimization of… (More)

During differentiation of lymphocytes into antibody-producing cells, an immunoglobulin kappa variable-region gene is transcriptionally activated by rearrangement linking it to a kappa constant (C kappa) region gene which is already transcribed prior to somatic rearrangement. The presence of a transcriptional enhancer element within the large intron of the… (More)

We investigate invariant random fields on the sphere using a new type of spherical wavelets, called needlets. These are compactly supported in frequency and enjoy excellent localization properties in real space, with quasi-exponentially decaying tails. We show that, for random fields on the sphere, the needlet coefficients are asymptotically uncorrelated… (More)

Usually, methods for thresholding wavelet estimators are implemented term by term, with empirical coecients included or excluded depending on whether their absolute values exceed a level that re¯ects plausible moderate deviations of the noise. We argue that performance may be improved by pooling coecients into groups and thresholding them together. This… (More)

We consider the problem of estimating an unknown function f in a regression setting with random design. Instead of expanding the function on a regular wavelet basis, we expand it on the basis {ψ jk (G), j, k} warped with the design. This allows to perform a very stable and computable thresholding algorithm. We investigate the properties of this new basis.… (More)