Neighbours list from knn object

The function converts a knn object returned by knearneigh into a neighbours list of class nb with a list of integer vectors containing neighbour region number ids.

Usage

knn2nb(knn, row.names = NULL, sym = FALSE)

Arguments

knn: A knn object returned by knearneigh
row.names: character vector of region ids to be added to the neighbours list as attribute region.id, default seq(1, nrow(x))
sym: force the output neighbours list to symmetry

Value

The function returns an object of class nb with a list of integer vectors containing neighbour region number ids. See card for details of “nb” objects.

Author

Roger Bivand Roger.Bivand@nhh.no

Examples

columbus <- st_read(system.file("shapes/columbus.gpkg", package="spData")[1], quiet=TRUE)
coords <- st_coordinates(st_centroid(columbus))
#> Warning: st_centroid assumes attributes are constant over geometries
col.knn <- knearneigh(coords, k=4)
plot(st_geometry(columbus), border="grey")
plot(knn2nb(col.knn), coords, add=TRUE)
title(main="K nearest neighbours, k = 4")

# example of reading points with readr::read_csv() yielding a tibble
load(system.file("etc/misc/coords.rda", package="spdep"))
class(coords)
#> [1] "spec_tbl_df" "tbl_df"      "tbl"         "data.frame" 
knn2nb(knearneigh(coords, k=4))
#> Neighbour list object:
#> Number of regions: 100 
#> Number of nonzero links: 400 
#> Percentage nonzero weights: 4 
#> Average number of links: 4 
#> Non-symmetric neighbours list