GEM can be run in 4 modes
MODE=1 is a GAM/K search for clustering
MODE=2 is the use of 2 K permutations of M GIS data layers to add general covariates in an attempt to destroy the clustering (the spatial epidemiologist approach)
MODE=3 examines 2 K permutations to find the strongest spatial associations with GIS layers that enhance the clustering (GCEM)
MODE=4 uses 2 K permutations to add local GIS covariates to destroy the cluster