  In addition to the $\lambda$ parameter, we have found another parameter which
characterize the class III, class II and class IV patterns more quantitatively.
It explains why the different classes of patterns coexist at the same
$\lambda$. With this parameter, the phase diagram for an one dimensional
cellular automata is obtained. Our result explains why the edge of chaos(class
IV) is scattered rather wide range in $\lambda$ around 0.5, and presents an
effective way to control the pattern classes. \noindent PACS: 89.75.-k Complex
Systems
