Spatial adjacency for a set of areas

Builds a neighbour list and row-standardised spatial weights for area polygons with spdep, for the spillover estimators and for Moran's I diagnostics. Queen contiguity (any shared point) is the default; rook contiguity needs a shared edge; knn links each area to its k nearest neighbours by centroid and symmetrises the result. Areas with no neighbours (islands) are allowed and counted.

Usage

lamp_adjacency(boundaries, method = c("queen", "rook", "knn"), k = 6L)

Arguments

boundaries

An sf polygon layer with an area column, for example from lamp_boundaries().

method

"queen" (default), "rook" or "knn".

k

Number of neighbours for method = "knn".

Value

A list of class lamp_adjacency with areas (identifiers in order), nb (an spdep neighbour list), listw (row-standardised weights, style = "W"), method, k, n_islands, boundary_vintage (taken from the vintage attribute of boundaries when present) and created.

See also

Other panel: lamp_adjacency_from_nb(), lamp_boundaries(), lamp_changelog(), lamp_coverage(), lamp_panel(), lamp_population(), lamp_revintage()

Examples

squares <- sf::st_sf(
  area = c("a", "b", "c"),
  geometry = sf::st_sfc(
    sf::st_polygon(list(rbind(c(0, 0), c(1, 0), c(1, 1), c(0, 1), c(0, 0)))),
    sf::st_polygon(list(rbind(c(1, 0), c(2, 0), c(2, 1), c(1, 1), c(1, 0)))),
    sf::st_polygon(list(rbind(c(5, 5), c(6, 5), c(6, 6), c(5, 6), c(5, 5)))),
    crs = 27700
  )
)
adj <- lamp_adjacency(squares)
adj
#> streetlamp adjacency: 3 areas, queen contiguity, 2 links, 1 island.
adj$nb
#> Neighbour list object:
#> Number of regions: 3 
#> Number of nonzero links: 2 
#> Percentage nonzero weights: 22.22222 
#> Average number of links: 0.6666667 
#> 1 region with no links:
#> c
#> 2 disjoint connected subgraphs