duckspatial (version 0.9.0)

ddbs_join: Performs spatial joins of two geometries

Description

Performs spatial joins of two geometries, and returns a sf object or creates a new table in a DuckDB database.

Usage

ddbs_join(
  x,
  y,
  join = "intersects",
  conn = NULL,
  name = NULL,
  crs = NULL,
  crs_column = "crs_duckspatial",
  overwrite = FALSE,
  quiet = FALSE
)

Value

an sf object or TRUE (invisibly) for table creation

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.

join

A geometry predicate function. Defaults to "intersects". See the details for other options.

conn

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

name

A character string of length one specifying the name of the table, or a character string of length two specifying the schema and table names. If it's NULL (the default), it will return the result as an sf object.

crs

The coordinates reference system of the data. Specify if the data doesn't have a crs_column, and you know the CRS.

crs_column

a character string of length one specifying the column storing the CRS (created automatically by ddbs_write_vector). Set to NULL if absent.

overwrite

Boolean. whether to overwrite the existing table if it exists. Defaults to FALSE. This argument is ignored when name is NULL.

quiet

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

Details

Spatial Join Predicates:

A spatial predicate is really just a function that evaluates some spatial relation between two geometries and returns true or false, e.g., “does a contain b” or “is a within distance x of b”. Here is a quick overview of the most commonly used ones, taking two geometries a and b:

• "ST_Intersects": Whether a intersects b

• "ST_Contains": Whether a contains b

• "ST_ContainsProperly": Whether a contains b without b touching a's boundary

• "ST_Within": Whether a is within b

• "ST_Overlaps": Whether a overlaps b

• "ST_Touches": Whether a touches b

• "ST_Equals": Whether a is equal to b

• "ST_Crosses": Whether a crosses b

• "ST_Covers": Whether a covers b

• "ST_CoveredBy": Whether a is covered by b

• "ST_DWithin": x) Whether a is within distance x of b

Examples

if (FALSE) {
# load packages
library(duckspatial)
library(sf)

# read polygons data
countries_sf <- sf::st_read(system.file("spatial/countries.geojson", package = "duckspatial"))

# create points data
n <- 100
points_sf <- data.frame(
    id = 1:n,
    x = runif(n, min = -180, max = 180),
    y = runif(n, min = -90, max = 90)
) |>
    sf::st_as_sf(coords = c("x", "y"), crs = 4326)



# option 1: passing sf objects
output1 <- duckspatial::ddbs_join(
    x = points_sf,
    y = countries_sf,
    join = "within"
)

plot(output1["CNTR_NAME"])


## option 2: passing the names of tables in a duckdb db

# creates a duckdb
conn <- duckspatial::ddbs_create_conn()

# write sf to duckdb
ddbs_write_vector(conn, points_sf, "points", overwrite = TRUE)
ddbs_write_vector(conn, countries_sf, "countries", overwrite = TRUE)

# spatial join
output2 <- ddbs_join(
    conn = conn,
    x = "points",
    y = "countries",
    join = "within"
)

plot(output2["CNTR_NAME"])

}