Each mesh element stores the number u(i,j) of tuples which belong to the mesh element (i,j) among data set D (u(i,j) is also called data number.) and the sum v(i,j) of values of the objective numeric attribute of tuples which belong to the mesh element (i,j) among data set D. Note that i is a coordinate value in the vertical axis and j is a coordinate value in the horizontal axis on the plane show