sp_weights: Create spatial weights from an sf object

In spopt: Spatial Optimization for Regionalization, Facility Location, and Market Analysis

Create spatial weights from an sf object

Description

Constructs spatial weights (neighborhood structure) from sf geometries. Wraps spdep functions with a convenient interface.

Usage

sp_weights(
  data,
  type = c("queen", "rook", "knn", "distance"),
  k = NULL,
  d = NULL,
  ...
)

Arguments

data	An sf object with polygon or point geometries.
type	Type of weights. One of: "queen" (default): Polygons sharing any boundary point are neighbors "rook": Polygons sharing an edge are neighbors "knn": K-nearest neighbors based on centroid distance "distance": All units within a distance threshold are neighbors
k	Number of nearest neighbors. Required when type = "knn".
d	Distance threshold. Required when type = "distance". Units match the CRS of the data (e.g., meters for projected CRS).
...	Additional arguments passed to spdep functions.

Details

Choosing a weight type:

• Use queen/rook for polygon data where physical adjacency matters

• Use knn when you need guaranteed connectivity (no isolates) or for point data

• Use distance for point data or when interaction depends on proximity

KNN weights always produce a connected graph (if k >= 1), making them useful for datasets with islands or disconnected polygons.

Value

A neighbors list object (class "nb") compatible with spdep.

Examples

library(sf)
nc <- st_read(system.file("shape/nc.shp", package = "sf"))

# Queen contiguity (default)
w_queen <- sp_weights(nc, type = "queen")

# K-nearest neighbors (guarantees connectivity)
w_knn <- sp_weights(nc, type = "knn", k = 6)

# Distance-based (e.g., 50km for projected data)
nc_proj <- st_transform(nc, 32119)  # NC State Plane
w_dist <- sp_weights(nc_proj, type = "distance", d = 50000)

spopt documentation built on April 22, 2026, 9:07 a.m.