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Spatial Filter

Source: R/ddbs_filter.R
ddbs_filter.Rd

Filters data spatially based on a spatial predicate

Usage

ddbs_filter(
  x,
  y,
  predicate = "intersects",
  conn = NULL,
  name = NULL,
  crs = NULL,
  crs_column = "crs_duckspatial",
  overwrite = FALSE,
  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

Y table with geometry column within the DuckDB database

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.

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 NULL (the default), the function returns 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 ignore when name is NULL.

quiet

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

Value

An sf object or TRUE (invisibly) for table creation

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) { # \dontrun{
## load packages
library(duckdb)
library(duckspatial)
library(sf)

# create a duckdb database in memory (with spatial extension)
conn <- ddbs_create_conn(dbdir = "memory")

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

## store in duckdb
ddbs_write_vector(conn, countries_sf, "countries")
ddbs_write_vector(conn, argentina_sf, "argentina")

## filter countries touching argentina
ddbs_filter(conn = conn, "countries", "argentina", predicate = "touches")

## filter without using a connection
ddbs_filter(countries_sf, argentina_sf, predicate = "touches")
} # }