Nonparametric regression with predictors missing at random and the scale depending on auxiliary covariates

Nonparametric regression with missing at random (MAR) predictors, univariate regression component of interest, and the scale function depending on both the predictor and auxiliary covariates, is considered. The asymptotic theory suggests that both heteroscedasticity and MAR mechanism affect the sharp constant of the minimax mean integrated squared error (MISE) convergence. We propose a data-driven procedure adaptive to the missing mechanism and unknown smoothness of the estimated regression function. The estimator preserves the optimal convergence rate and can achieve sharp minimaxity when predictors are missing completely at random (MCAR).