Compute Distance Matrix

Pre-compute pairwise distances between sites for reuse across multiple spacc() calls. Supports sf objects with accurate geodesic distances for global-scale studies.

Usage

distances(x, method = NULL, fun = NULL, which = NULL)

Arguments

x

Site locations. Can be:

• A data.frame with columns x and y

• An sf object with POINT geometries

• An sfc_POINT object

method

Character. Distance method:

• "euclidean": Euclidean distance (for projected coordinates)

• "haversine": Great-circle distance (for lat/lon, fast approximation

• "geodesic": Accurate ellipsoidal distance via sf/S2 (for global scale) Default is auto-detected from CRS when using sf objects.

fun

Optional custom distance function. Must take two coordinate vectors (x, y) and return a distance matrix. Overrides method.

which

For sf objects, column name containing the geometry. Default uses active geometry.

Value

An object of class spacc_dist containing the distance matrix with coordinates stored as an attribute.

Details

For continental and global-scale studies, use sf objects with geographic CRS (e.g., EPSG:4326). The function will automatically use accurate geodesic distances via the S2 spherical geometry library.

For smaller study areas with projected coordinates (UTM, etc.), Euclidean distance is appropriate and faster.

Examples

# \donttest{
coords <- data.frame(x = runif(50), y = runif(50))
d <- distances(coords)

# Reuse for multiple analyses
species <- matrix(rbinom(50 * 30, 1, 0.3), nrow = 50)
sac <- spacc(species, d)
# }