duckspatial (version 0.9.0)

ddbs_envelope: Returns the envelope (bounding box) of geometries

Description

Returns the minimum bounding rectangle (envelope) of geometries from a sf object or a DuckDB table. Returns the result as an sf object or creates a new table in the database.

Usage

ddbs_envelope(
  x,
  by_feature = FALSE,
  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.

by_feature

Logical. If TRUE, returns one envelope per feature. If FALSE (default), returns a single envelope for all geometries combined.

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 ignored when name is NULL.

quiet

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

Details

ST_Envelope returns the minimum bounding rectangle (MBR) of a geometry as a polygon. For points and lines, this creates a rectangular polygon that encompasses the geometry. For polygons, it returns the smallest rectangle that contains the entire polygon.

When by_feature = FALSE, all geometries are combined and a single envelope is returned that encompasses the entire dataset.

Examples

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

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

# input as sf, and output as sf
env <- ddbs_envelope(x = argentina_sf, by_feature = TRUE)

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

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

# envelope for each feature
env <- ddbs_envelope("argentina", conn, by_feature = TRUE)

# single envelope for entire dataset
env_all <- ddbs_envelope("argentina", conn, by_feature = FALSE)

# create a new table with envelopes
ddbs_envelope("argentina", conn, name = "argentina_bbox", by_feature = TRUE)
}