An updated algorithm for fast computing positive region

Positive region is the one of the core concepts in rough set theory, which algorithm complexity of region directly affects other algorithms. With a equivalent definition of area, this paper proposes a calculation method based on the diagonal matrix. This method stores the compatible object set searched every time in the diagonal of diagonal matrix, and the object searched has to be zero processed, thereby the method reduces the amount of computation. Examples show that the method convenient, simple and intuitive, and can improve the of computing positive region.