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{
# Load a complete simulated planning problem.
example_data <- load_sim_multiaction()

p <- create_problem(
  pu = example_data$planning_units,
  features = example_data$features,
  dist_features = example_data$dist_features,
  cost = "cost"
)

p <- add_spatial_queen(
  x = p,
  geometry = example_data$planning_units,
  name = "queen",
  weight = 1
)

head(p$data$spatial_relations$queen)
#>   internal_pu1 internal_pu2 weight pu1 pu2   source relation_name directed
#> 1            1            2      1   1   2 queen_sf         queen    FALSE
#> 2            1            9      1   1   9 queen_sf         queen    FALSE
#> 3            1           10      1   1  10 queen_sf         queen    FALSE
#> 4            2            3      1   2   3 queen_sf         queen    FALSE
#> 5            2            9      1   2   9 queen_sf         queen    FALSE
#> 6            2           10      1   2  10 queen_sf         queen    FALSE
# }