spam (version 0.20-3)

UScounties: Adjacency structure of the counties in the contiguous United States

Description

First and second order adjacency structure of the counties in the contiguous United States. We consider that two counties are neighbors if they share at least one edge of their polygon description in maps.

See Also

map

Examples

# number of counties:
n  <- nrow( UScounties.storder)

# make a precision matrix 
Q <- diag.spam( n) + .2 * UScounties.storder + .1 * UScounties.ndorder
display( as.spam( chol( Q)))