Add queen adjacency from polygons

Build and register a queen adjacency relation from planning-unit polygons.

Two planning units are queen-adjacent if their boundaries touch, either along a shared edge or at a shared vertex.

Usage

add_spatial_queen(x, geometry = NULL, name = "queen", weight = 1)

Arguments

x

A Problem object created with create_problem or another object containing aligned planning-unit polygons.

geometry

Optional sf object with planning-unit polygons and an id column. If NULL, x$data$pu_sf is used.

name

Character string giving the key under which the relation is stored.

weight

Numeric scalar giving the edge weight assigned to each queen adjacency.

Value

An updated Problem object.

Details

Use this function when neighbourhood should include both shared edges and corner-touching polygon contacts.

This constructor derives an adjacency graph from polygon geometry using a queen criterion. If planning units \(i\) and \(j\) touch at any boundary point, then an edge \((i,j)\) is added to the relation.

Let \(G = (\mathcal{I}, E)\) denote the resulting graph. Then: $$ (i,j) \in E \quad \Longleftrightarrow \quad \partial i \cap \partial j \neq \varnothing. $$

Thus, queen adjacency includes all rook neighbours plus corner-touching neighbours.

All edges receive the same user-supplied weight.

The resulting relation is stored as an undirected spatial relation.

See also

add_spatial_rook, add_spatial_boundary

Examples

# \donttest{
library(terra)
#> Warning: package 'terra' was built under R version 4.4.3
#> terra 1.8.80

data("sim_pu_sf", package = "multiscape")
sim_features <- load_sim_features_raster()

p <- create_problem(
  pu = sim_pu_sf,
  features = sim_features,
  cost = "cost"
)

p <- add_spatial_queen(
  x = p,
  geometry = sim_pu_sf,
  name = "queen",
  weight = 1
)

head(p$data$spatial_relations$queen)
#>       internal_pu1 internal_pu2 weight   pu1   pu2   source relation_name
#> 27430        10000        10001      1 10000 10001 queen_sf         queen
#> 27431        10000        10132      1 10000 10132 queen_sf         queen
#> 27432        10000        10133      1 10000 10133 queen_sf         queen
#> 27433        10001        10002      1 10001 10002 queen_sf         queen
#> 27434        10001        10133      1 10001 10133 queen_sf         queen
#> 27435        10001        10134      1 10001 10134 queen_sf         queen
# }