Unambiguous Neighborhoods with sfdep

Initialization Code

library(tidyverse) |> suppressPackageStartupMessages()
library(mapview) |> suppressPackageStartupMessages()
library(rnaturalearth) |> suppressPackageStartupMessages()
library(spdep) |> suppressPackageStartupMessages()

• Relevant Moraga
• Relevant Pebesma

Finding Neighbors in Asia

asia_countries_sf <- ne_countries(continent = "Asia", scale=50)
mapview(asia_countries_sf, label="geounit")

library(spdep)
asia_countries_nb <- asia_countries_sf |>
  spdep::poly2nb(
    queen = TRUE,
    row.names=asia_countries_sf$geounit
  )
asia_countries_nb

Neighbour list object:
Number of regions: 53 
Number of nonzero links: 164 
Percentage nonzero weights: 5.838377 
Average number of links: 3.09434 
7 regions with no links:
Taiwan Sri Lanka Singapore Philippines Japan Bahrain Indian Ocean
Territories
9 disjoint connected subgraphs

nb_cents <- sf::st_point_on_surface(asia_countries_sf) |>
  sf::st_as_sf()

Warning: st_point_on_surface assumes attributes are constant over geometries

Warning in st_point_on_surface.sfc(st_geometry(x)): st_point_on_surface may not
give correct results for longitude/latitude data

nb_lines <- spdep::nb2lines(
  asia_countries_nb,
  coords=st_coordinates(nb_cents),
  as_sf=TRUE
)
nb_lines$edgelabel <- paste0(nb_lines$i_ID, "-", nb_lines$j_ID)
mapview(nb_cents, label="geounit") + mapview(nb_lines, label="edgelabel")

print(asia_countries_nb)

Neighbour list object:
Number of regions: 53 
Number of nonzero links: 164 
Percentage nonzero weights: 5.838377 
Average number of links: 3.09434 
7 regions with no links:
Taiwan Sri Lanka Singapore Philippines Japan Bahrain Indian Ocean
Territories
9 disjoint connected subgraphs

asia_nb_names <- attributes(asia_countries_nb)$region.id
afg_index <- which(asia_nb_names == "Afghanistan")
asia_countries_sf$neighbors <- "other"
asia_countries_sf$neighbors[afg_index] <- "area"
asia_countries_sf$neighbors[asia_countries_nb[[afg_index]]] <- "neighbors"
afg_sf <- asia_countries_sf |> filter(neighbors != "other")
ggplot(afg_sf) +
  geom_sf(aes(fill = neighbors)) +
  theme_bw() +
  scale_fill_manual(
    values = c("gray30", "gray", "white")
  )

mapview(afg_sf, zcol="neighbors", label="geounit")

nb_weights <- asia_countries_nb |>
  spdep::nb2listw(zero.policy=TRUE)

afg_df <- tibble(
  nb_name=asia_countries_sf$geounit[nb_weights$neighbours[[afg_index]]],
  nb_index=nb_weights$neighbours[[afg_index]],
  nb_weight=nb_weights$weights[[afg_index]]
)
afg_df

nb_name	nb_index	nb_weight
Uzbekistan	3	0.1666667
Turkmenistan	5	0.1666667
Tajikistan	9	0.1666667
Pakistan	18	0.1666667
Iran	34	0.1666667
China	40	0.1666667

nb_dist_weights <- asia_countries_nb |>
  spdep::nb2listwdist(nb_cents, zero.policy=TRUE)

afg_dist_df <- tibble(
  nb_name=asia_countries_sf$geounit[nb_dist_weights$neighbours[[afg_index]]],
  nb_index=nb_dist_weights$neighbours[[afg_index]],
  nb_weight=nb_dist_weights$weights[[afg_index]]
)
afg_dist_df

nb_name	nb_index	nb_weight
Uzbekistan	3	0.1306825
Turkmenistan	5	0.1251905
Tajikistan	9	0.1321491
Pakistan	18	0.1657872
Iran	34	0.0890133
China	40	0.0298321