Build distance matrix from longitude/latitude coordinates

This function builds the pairwise distance matrix (in kilometers) from vectors of longitude (x) and latitude (y), either by planar approximation or great-circle (Haversine) formula.

Usage

get_distance_matrix(x, y, id, method = c("spherical", "planar"), sort = TRUE)

Arguments

x

Numeric vector of longitudes (degrees).

y

Numeric vector of latitudes (degrees).

id

Character vector of names for each location.

method

Character string, either "spherical" (default) for Haversine distances on a sphere of radius 6371 km, or "planar" for Euclidean distances in degree‐space converted by 111.35 km/deg.

sort

Logical. When TRUE (default, preserving historical behavior) the returned matrix is sorted alphabetically by id. When FALSE the rows/columns are kept in the order of id (config order), so the axes stay aligned to any value vector indexed the same way. Set FALSE for the spatial-figures path, where labels must follow config order rather than be silently re-sorted (F3).

Value

A square matrix of pairwise distances (km) among locations, with row and column names from id. By default sorted alphabetically; when sort = FALSE, kept in id (input) order.

Examples

if (FALSE) { # \dontrun{
# Sample lon/lat for three cities
lon <- c(-122.33, -118.24, -74.00)
lat <- c(  47.61,   34.05,   40.71)
id  <- c("Seattle", "LosAngeles", "NewYork")

# 1. Great‐circle (Haversine) distances in km
D_spherical <- get_distance_matrix(lon, lat, id)

# 2. Planar approximation (× 111.35 km/deg)
D_planar <- get_distance_matrix(lon, lat, id, method = "planar")

# Inspect results
print(D_spherical)
print(D_planar)
} # }