UScounties {spam} | R Documentation

## 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`.

### Format

Two matrices of class `spam`

UScounties.storder

  Contains a one in the `i` and `j` element if county `i` is a neighbor of county `j`.

UScounties.ndorder

  Contains a one in the `i` and `j` element if counties `i` and `j` are a neighbors of county `k` and counties `i` and `j` are not neighbors.

### See Also

`map` from maps.

### Examples

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

    ## Not run:
    # make a precision matrix
    Q <- diag.spam( n) + .2 * UScounties.storder + .1 * UScounties.ndorder
    display( as.spam( chol( Q)))

    ## End(Not run)

[Package spam version 2.2-2 Index]