Prepare SaTScan Geometry File

Usage

prep_geo(
  x,
  loc_id,
  coords = NULL,
  geometry = NULL,
  coord_type = c("auto", "latlong", "cartesian")
)

Arguments

x

Input object. Can be an sf object or a data.frame.

loc_id

Column name for location ID (unquoted).

coords

Character vector of length 2 specifying coordinate columns if x is a data.frame.

geometry

Column name for geometry if x is sf and not active geometry (optional).

coord_type

Coordinate system: "auto" (default), "latlong", or "cartesian".

• "auto": Attempts to detect from data range or CRS.

• "latlong": Forces interpretation as Latitude/Longitude.

• "cartesian": Forces interpretation as Cartesian (X/Y).

Value

A satscan_table object of kind "geo".

Details

Prepares a coordinate file for SaTScan. Handles sf objects (extracting centroids) or plain data frames.

SaTScan File Specification

The Coordinates File has the following structure: <LocationID> <Latitude/Y> <Longitude/X>

• LocationID: Unique identifier matching Case/Population files.

• Coordinate Order:

  • Lat/Long: SaTScan expects Latitude first, then Longitude.

  • Cartesian: SaTScan expects X first, then Y.

Note on Coordinate Ordering: This function automatically handles the swapping for you:

• If sf object (Lat/Long crs) -> Swaps to Lat, Long.

• If data.frame (Lat/Long detected) -> Swaps to Lat, Long.

• If data.frame (Cartesian detected) -> Keeps as X, Y.

See also

ss_geo() for the new ss_tbl interface.

Examples

if (FALSE) { # \dontrun{
# From sf object
library(sf)
my_shapes <- st_read("shapes.shp")
geo_obj <- prep_geo(my_shapes, loc_id = GEOID)

# From data frame (Lat/Long)
df <- data.frame(id = "A", lon = 100, lat = 13)
geo_obj2 <- prep_geo(df, loc_id = id, coords = c("lon", "lat"), coord_type = "latlong")

# From data frame (Cartesian)
df_cart <- data.frame(id = "A", x = 500000, y = 100000)
geo_obj3 <- prep_geo(df_cart, loc_id = id, coords = c("x", "y"), coord_type = "cartesian")
} # }