Mapcurves: a quantitative method for comparing categorical maps.
mapcurves(x, y, z = NULL)
A list with two elements:
"ref_map" - the map to be used as reference ("x" or "y")
"gof" - the Mapcurves's goodness of fit value
Hargrove, William W., Forrest M. Hoffman, and Paul F. Hessburg. "Mapcurves: a quantitative method for comparing categorical maps." Journal of Geographical Systems 8.2 (2006): 187.