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Union of geometries

Source: R/ddbs_combine.R
ddbs_union.Rd

Computes the union of geometries from a sf objects or a DuckDB tables using. This is equivalent to sf::st_union(). The function supports three modes: (1) union all geometries from a single object into one geometry, (2) union geometries from a single object grouped by one or more columns, (3) union geometries from two different objects. Returns the result as an sf object or creates a new table in the database.

Usage

ddbs_union(
  x,
  y = NULL,
  by = NULL,
  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

optional. A second table name, sf object, or DuckDB connection to compute the pairwise union between geometries in x and y. Default is NULL

by

optional. Character vector specifying one or more column names to group by when computing unions. Geometries will be unioned within each group. Default is NULL

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

character string specifying the name of the CRS column. Default is "crs_duckspatial"

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.

Value

an sf object or TRUE (invisibly) for table creation

Examples

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

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

# read data
rivers_sf <- st_read(system.file("spatial/rivers.geojson", package = "duckspatial"))

# store in duckdb
ddbs_write_vector(conn, rivers_sf, "rivers")

# union all geometries into one
ddbs_union(conn = conn, "rivers")

# union without using a connection
ddbs_union(rivers_sf)

# union geometries grouped by a column
ddbs_union(conn = conn, "rivers", by = "RIVER_NAME")

# store result in a new table
ddbs_union(conn = conn, "rivers", name = "rivers_union")
} # }