Drop links in a neighbours list

Drops links to and from or just to a region from a neighbours list. The example corresponds to Fingleton's Table 1, p. 6, for lattices 5 to 19.

droplinks(nb, drop, 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

Value

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

Roger Bivand Roger.Bivand@nhh.no

See also

is.symmetric.nb

Examples

# \donttest{
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)
#>         0.2      0.5      0.95     0.999          1
#> 5  1.038271 1.312627  9.486051  30.81487   32.04915
#> 7  1.036443 1.295621 10.899580  83.25437   92.09812
#> 9  1.035356 1.285145 10.798611 160.90951  195.02166
#> 11 1.034639 1.278279 10.383083 254.83998  347.71145
#> 13 1.034132 1.273442  9.968389 353.66366  555.88699
#> 15 1.033753 1.269852  9.619387 447.19245  824.46560
#> 17 1.033460 1.267082  9.337167 528.49015 1157.77630
#> 19 1.033227 1.264879  9.109487 594.23907 1559.69614
print(mxs)
#>         0.2      0.5     0.95     0.999          1
#> 5  1.048834 1.401934 12.00215  39.22742   40.79967
#> 7  1.048834 1.402174 14.66823 106.90031  118.01556
#> 9  1.048834 1.402176 15.49606 207.28928  249.74893
#> 11 1.048834 1.402176 15.75744 329.22973  443.97194
#> 13 1.048834 1.402176 15.83957 458.75739  707.14827
#> 15 1.048834 1.402176 15.86474 583.50722 1044.75562
#> 17 1.048834 1.402176 15.87225 695.10288 1461.57017
#> 19 1.048834 1.402176 15.87445 789.50575 1961.84025

# }