Subset a neighbours list

The function subsets a neighbors list, retaining objects for which the subset argument vector is TRUE.

# S3 method for nb
subset(x, subset, ...)

Arguments

x

an object of class nb

subset

logical expression

...

generic function pass-through

Value

The function returns an object of class nb with a list of integer vectors containing neighbour region number ids (compacted to run from 1:number of regions in subset).

Author

Roger Bivand Roger.Bivand@nhh.no

See also

nb2listw

Examples

columbus <- st_read(system.file("shapes/columbus.shp", package="spData")[1], quiet=TRUE)
col.gal.nb <- read.gal(system.file("weights/columbus.gal", package="spData")[1])
coords <- st_coordinates(st_centroid(columbus))
#> Warning: st_centroid assumes attributes are constant over geometries
plot(col.gal.nb, coords)
to.be.dropped <- c(31, 34, 36, 39, 42, 46)
text(coords[to.be.dropped,1], coords[to.be.dropped,2], labels=to.be.dropped,
  pos=2, offset=0.3)
sub.col.gal.nb <- subset(col.gal.nb,
  !(1:length(col.gal.nb) %in% to.be.dropped))
plot(sub.col.gal.nb, coords[-to.be.dropped,], col="red", add=TRUE)

which(!(attr(col.gal.nb, "region.id") %in%
  attr(sub.col.gal.nb, "region.id")))
#> [1] 31 34 36 39 42 46