Characteristic Representation of Elementary Cellular Automata

We propose a characteristic representation ofone-dimensional and 2-state, 3-neighbor cellular automaton rules, which describes an effective form of each rule after many time steps. Simulated results of the representation show that complex structures of Class IV rules come from their aspects of Class II and III. Class IV-like patterns can be generated by characteristic functions of a linear combenation of Class II and III rule functions.