1-penalized quantile regression in high-dimensional sparse models
Belloni, Alexandre ; Chernozhukov, Victor
Ann. Statist., Tome 39 (2011) no. 1, p. 82-130 / Harvested from Project Euclid
We consider median regression and, more generally, a possibly infinite collection of quantile regressions in high-dimensional sparse models. In these models, the number of regressors p is very large, possibly larger than the sample size n, but only at most s regressors have a nonzero impact on each conditional quantile of the response variable, where s grows more slowly than n. Since ordinary quantile regression is not consistent in this case, we consider ℓ1-penalized quantile regression (ℓ1-QR), which penalizes the ℓ1-norm of regression coefficients, as well as the post-penalized QR estimator (post-ℓ1-QR), which applies ordinary QR to the model selected by ℓ1-QR. First, we show that under general conditions ℓ1-QR is consistent at the near-oracle rate $\sqrt{s/n}\sqrt{\log(p\vee n)}$ , uniformly in the compact set $\mathcal{U}\subset(0,1)$ of quantile indices. In deriving this result, we propose a partly pivotal, data-driven choice of the penalty level and show that it satisfies the requirements for achieving this rate. Second, we show that under similar conditions post-ℓ1-QR is consistent at the near-oracle rate $\sqrt{s/n}\sqrt{\log(p\vee n)}$ , uniformly over $\mathcal{U}$ , even if the ℓ1-QR-selected models miss some components of the true models, and the rate could be even closer to the oracle rate otherwise. Third, we characterize conditions under which ℓ1-QR contains the true model as a submodel, and derive bounds on the dimension of the selected model, uniformly over $\mathcal{U}$ ; we also provide conditions under which hard-thresholding selects the minimal true model, uniformly over $\mathcal{U}$ .
Publié le : 2011-02-15
Classification:  Median regression,  quantile regression,  sparse models,  62H12,  62J99,  62J07
@article{1291388370,
     author = {Belloni, Alexandre and Chernozhukov, Victor},
     title = {l<sub>1</sub>-penalized quantile regression in high-dimensional sparse models},
     journal = {Ann. Statist.},
     volume = {39},
     number = {1},
     year = {2011},
     pages = { 82-130},
     language = {en},
     url = {http://dml.mathdoc.fr/item/1291388370}
}
Belloni, Alexandre; Chernozhukov, Victor. ℓ1-penalized quantile regression in high-dimensional sparse models. Ann. Statist., Tome 39 (2011) no. 1, pp.  82-130. http://gdmltest.u-ga.fr/item/1291388370/