  In this paper, we give a generalization of the rough topology and the core to
numerical data by classifying objects in terms of the attribute values. New
approach to find the core for numerical data is discussed. Then a measurement
to find whether an attribute is in the core or not is given. This new method
for finding the core is used for attribute reduction. It is tested and compared
by using machine learning algorithms. Finally, the algorithms and codes to
convert a data to pertinent data and to find core is also provided.
