Add rook adjacency from polygons

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

Two planning units are rook-adjacent if they share a boundary segment of positive length. Corner-only contact does not count as rook adjacency.

Usage

add_spatial_rook(x, geometry = NULL, name = "rook", 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 rook adjacency.

Value

An updated Problem object.

Details

Use this function when neighbourhood should be defined by shared polygon edges rather than by point-touching or coordinate-based proximity.

This constructor derives an adjacency graph from polygon geometry using a rook criterion. If planning units \(i\) and \(j\) share a common edge of non-zero length, then an edge \((i,j)\) is added to the relation.

Let \(G = (\mathcal{I}, E)\) denote the resulting graph. Then: $$ (i,j) \in E \quad \Longleftrightarrow \quad \mathrm{length}(\partial i \cap \partial j) > 0. $$

All edges receive the same user-supplied weight.

The resulting relation is stored as an undirected spatial relation.

See also

add_spatial_queen, 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_rook(
  x = p,
  geometry = example_data$planning_units,
  name = "rook",
  weight = 1
)

head(p$data$spatial_relations$rook)
#>   internal_pu1 internal_pu2 weight pu1 pu2  source relation_name directed
#> 1            1            2      1   1   2 rook_sf          rook    FALSE
#> 2            1            9      1   1   9 rook_sf          rook    FALSE
#> 3            2            3      1   2   3 rook_sf          rook    FALSE
#> 4            2           10      1   2  10 rook_sf          rook    FALSE
#> 5            3            4      1   3   4 rook_sf          rook    FALSE
#> 6            3           11      1   3  11 rook_sf          rook    FALSE
# }