droplinks {spdep} | R Documentation

## Drop links in a neighbours list

### Description

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.

### Usage

    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.

### Author(s)

Roger Bivand Roger.Bivand@nhh.no

### 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.

### 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)

[Package spdep version 0.4-56 Index]