Quantitative estimates in approximation by Bernstein-Durrmeyer-Choquet operators with respect to monotone and submodular set functions

Abstract: For the qualitative results of pointwise and uniform approximation obtained in \cite{Gal-Opris}, we present general quantitative estimates in terms of the modulus of continuity and in terms of a $K$-functional, for the generalized multivariate Bernstein-Durrmeyer operator $M_{n, \Gamma_{n, x}}$, written in terms of the Choquet integral with respect to a family of monotone and submodular set functions, $\Gamma_{n, x}$, on the standard $d$-dimensional simplex. When $\Gamma_{n, x}$ reduces to two elements, one a Choquet submodular set function and the other one a Borel measure, for suitable modified Bernstein-Durrmeyer operators, univariate $L^{p}$-approximations, $p\ge 1$, with estimates in terms of a $K$-functional are proved. In the particular cases when $d=1$ and the Choquet integral is taken with respect to some concrete possibility measures, the pointwise estimate in terms of the modulus of continuity is detailed. Some simple concrete examples of operators improving the classical error estimates are presented. Potential applications to practical methods dealing with data, like learning theory and regression models, also are mentioned.