droplinks function

Drop and add links in a neighbours list

droplinks drops links to and from or just to a region from a neighbours list. The example corresponds to Fingleton's Table 1, (1999) p. 6, for lattices 5 to 19. addlinks1 adds links from a single region to specified regions.

droplinks(nb, drop, sym=TRUE)
addlinks1(nb, from, to, sym=TRUE)

Arguments

• nb: a neighbours list object of class nb
• drop: either a logical vector the length of nb, or a character vector of named regions corresponding to nb's region.id attribute, or an integer vector of region numbers
• sym: TRUE for removal of both "row" and "column" links, FALSE for only "row" links; when adding links, inserts links to the from region from the to regions
• from: single from region for adding links, either a character vector of length 1 of the named from region corresponding to nb's region.id attribute, or an integer vector of length 1 holding a region number
• to: to regions, either a character vector of named from regions corresponding to nb's region.id attribute, or an integer vector of region numbers

Returns

The function returns an object of class nb with a list of integer vectors containing neighbour region number ids.

References

B. Fingleton (1999) Spurious spatial regression: some Monte Carlo results with a spatial unit root and spatial cointegration, Journal of Regional Science 39, pp. 1--19.

Author(s)

Roger Bivand Roger.Bivand@nhh.no

See Also

is.symmetric.nb

Examples

rho <- c(0.2, 0.5, 0.95, 0.999, 1.0)
ns <- c(5, 7, 9, 11, 13, 15, 17, 19)
mns <- matrix(0, nrow=length(ns), ncol=length(rho))
rownames(mns) <- ns
colnames(mns) <- rho
mxs <- matrix(0, nrow=length(ns), ncol=length(rho))
rownames(mxs) <- ns
colnames(mxs) <- rho
for (i in 1:length(ns)) {
  nblist <- cell2nb(ns[i], ns[i])
  nbdropped <- droplinks(nblist, ((ns[i]*ns[i])+1)/2, sym=FALSE)
  listw <- nb2listw(nbdropped, style="W", zero.policy=TRUE)
  wmat <- listw2mat(listw)
  for (j in 1:length(rho)) {
    mat <- diag(ns[i]*ns[i]) - rho[j] * wmat
    res <- diag(solve(t(mat) %*% mat))
    mns[i,j] <- mean(res)
    mxs[i,j] <- max(res)
  }
}
print(mns)
print(mxs)