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.

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

See also

knearneigh, card

Examples

columbus <- st_read(system.file("shapes/columbus.shp", package="spData")[1], quiet=TRUE)
coords <- coordinates(as(columbus, "Spatial"))
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