In a recent article, Noh, El Ghouch, and Bouezmarni proposed a new semiparametric estimate of a regression function with a multivariate predictor, which is based on a specification of the dependence structure between the predictor and the response by means of a parametric copula. This comment...

We propose rank-based estimators of principal components, both in the one-sample and, under the assumption of <italic>common principal components</italic>, in the <italic>m</italic>-sample cases. Those estimators are obtained via a rank-based version of Le Cam's one-step method, combined with an estimation of <italic>cross-information...</italic>

Despite their importance, optimal designs for quantile regression models have not been developed so far. In this article, we investigate the <italic>D</italic>-optimal design problem for nonlinear quantile regression analysis. We provide a necessary condition to check the optimality of a given design and use it...