Given an initial condition sequence with density , this Demonstration measures density of the last steps of the elementary cellular automata rule . The abscissa is the input and the ordinate is the output density. A typical evolution of the corresponding rule is shown to the right of the density map.

Consider the identity rule , 204. The density map is a 45 degree line, indicating that the density is preserved—which is a property of the identity rule, as well as the left and right shift rules (rules 170 and 240, respectively).