Mixture of Regression Models with Single-Index
  In this article, we propose a class of semiparametric mixture regression models with single-index. We argue that many recently proposed semiparametric/nonparametric mixture regression models can be considered special cases of the proposed model. However, unlike existing semiparametric mixture regression models, the new pro- posed model can easily incorporate multivariate predictors into the nonparametric components. Backfitting estimates and the corresponding algorithms have been proposed for to achieve the optimal convergence rate for both the parameters and the nonparametric functions. We show that nonparametric functions can be esti- mated with the same asymptotic accuracy as if the parameters were known and the index parameters can be estimated with the traditional parametric root n convergence rate. Simulation studies and an application of NBA data have been conducted to demonstrate the finite sample performance of the proposed models. 
Sijia Xiang and Weixin Yao
stat.ME