Fuzzy derivative and its applications to data classification

We introduce a method to describe a relationship between two parameters, based on the notion of a fuzzy derivative. This definition is quite different from the same notions used in the literature, where fuzzy derivatives are defined via a reformulation of the notion of derivative in classic mathematics. In this work this notation appears as a mathematical tool for describing a relationship between parameters. The main idea is to describe the influence of the change of one parameter on another. The suggested method is mainly directed to studying systems with qualitative features, but it also can be used for systems with quantitative features. The proposed method is applied to classification in the liver-disorder database