Configurations and reaction updating with sample classes.

(a) Initial configuration with sample indices and neighborhood configurations. Note that the number of adjacent open sites can be inferred from the number of foxes and rabbits. (b) Updating the neighborhood and sample indices after a reaction. Suppose the highlighted fox and rabbit sites undergo a predation event. The rabbit is replaced with a fox, and so the neighborhood and sample indices of the sites surrounding the former R require updating to reflect the new configuration. The sample indices of the new F will change as well, but its neighborhood index will not. This update procedure need only be done for and around sites that change species.