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Spatial predicate operations

Source: R/ddbs_predicates.R
ddbs_predicate.Rd

Computes spatial relationships between two geometry datasets using DuckDB's spatial extension. Returns a list where each element corresponds to a row of x, containing the indices (or IDs) of rows in y that satisfy the specified spatial predicate.

Usage

ddbs_predicate(
  x,
  y,
  predicate = "intersects",
  conn = NULL,
  id_x = NULL,
  id_y = NULL,
  sparse = TRUE,
  distance = NULL,
  quiet = FALSE
)

Arguments

x

An sf spatial object. Alternatively, it can be a string with the name of a table with geometry column within the DuckDB database conn. Data is returned from this object.

y

An sf spatial object. Alternatively, it can be a string with the name of a table with geometry column within the DuckDB database conn. Data is returned from this object.

predicate

A geometry predicate function. Defaults to intersects, a wrapper of ST_Intersects. See details for other options.

conn

A connection object to a DuckDB database. If NULL, the function runs on a temporary DuckDB database.

id_x

Character; optional name of the column in x whose values will be used to name the list elements. If NULL, integer row numbers of x are used.

id_y

Character; optional name of the column in y whose values will replace the integer indices returned in each element of the list.

sparse

A logical value. If TRUE, it returns a sparse index list. If FALSE, it returns a dense logical matrix.

distance

a numeric value specifying the distance for ST_DWithin. Units correspond to the coordinate system of the geometry (e.g. degrees or meters)

quiet

A logical value. If TRUE, suppresses any informational messages. Defaults to FALSE.

Value

A list of length equal to the number of rows in x.

  • Each element contains:

    • integer vector of row indices of y that satisfy the predicate with the corresponding geometry of x, or

    • character vector if id_y is supplied.

  • The names of the list elements:

    • are integer row numbers of x, or

    • the values of id_x if provided.

If there's no match between x and y it returns NULL

Details

This function provides a unified interface to all spatial predicate operations in DuckDB's spatial extension. It performs pairwise comparisons between all geometries in x and y using the specified predicate.

Available Predicates

  • intersects: Geometries share at least one point

  • covers: Geometry x completely covers geometry y

  • touches: Geometries share a boundary but interiors do not intersect

  • disjoint: Geometries have no points in common

  • within: Geometry x is completely inside geometry y

  • dwithin: Geometry x is completely within a distance of geometry y

  • contains: Geometry x completely contains geometry y

  • overlaps: Geometries share some but not all points

  • crosses: Geometries have some interior points in common

  • equals: Geometries are spatially equal

  • covered_by: Geometry x is completely covered by geometry y

  • intersects_extent: Bounding boxes of geometries intersect (faster but less precise)

  • contains_properly: Geometry x contains geometry y without boundary contact

  • within_properly: Geometry x is within geometry y without boundary contact

If x or y are not DuckDB tables, they are automatically copied into a temporary in-memory DuckDB database (unless a connection is supplied via conn).

id_x or id_y may be used to replace the default integer indices with the values of an identifier column in x or y, respectively.

Examples

if (FALSE) { # \dontrun{
## Load packages
library(duckspatial)
library(dplyr)
library(sf)

## create in-memory DuckDB database
conn <- ddbs_create_conn(dbdir = "memory")

## read countries data, and rivers
countries_sf <- read_sf(system.file("spatial/countries.geojson", package = "duckspatial")) |>
  filter(CNTR_ID %in% c("PT", "ES", "FR", "IT"))
rivers_sf <- st_read(system.file("spatial/rivers.geojson", package = "duckspatial")) |>
  st_transform(st_crs(countries_sf))

## Store in DuckDB
ddbs_write_vector(conn, countries_sf, "countries")
ddbs_write_vector(conn, rivers_sf, "rivers")

## Example 1: Check which rivers intersect each country
ddbs_predicate(countries_sf, rivers_sf, predicate = "intersects", conn)

## Example 2: Find neighboring countries
ddbs_predicate(countries_sf, countries_sf, predicate = "touches",
               id_x = "NAME_ENGL", id_y = "NAME_ENGL")

## Example 3: Find rivers that don't intersect countries
ddbs_predicate(countries_sf, rivers_sf, predicate = "disjoint",
               id_x = "NAME_ENGL", id_y = "RIVER_NAME")

## Example 4: Use table names inside duckdb
ddbs_predicate("countries", "rivers", predicate = "within", conn, "NAME_ENGL")
} # }