Skip to contents

Get the envelope (bounding box) of geometries

Source: R/ddbs_extent_funs.R
ddbs_envelope.Rd

Returns the minimum axis-aligned rectangle that fully contains the geometry.

Usage

ddbs_envelope(
  x,
  by_feature = FALSE,
  conn = NULL,
  name = NULL,
  crs = NULL,
  crs_column = "crs_duckspatial",
  mode = NULL,
  overwrite = FALSE,
  quiet = FALSE
)

Arguments

x

Input spatial data. Can be:

  • A duckspatial_df object (lazy spatial data frame via dbplyr)

  • An sf object

  • A tbl_lazy from dbplyr

  • A character string naming a table/view in conn

Data is returned from this object.

by_feature

Logical. If TRUE, the geometric operation is applied separately to each geometry. If FALSE, the geometric operation is applied to the data as a whole.

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

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

crs_column

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

mode

Character. Controls the return type. Options:

  • "duckspatial" (default): Lazy spatial data frame backed by dbplyr/DuckDB

  • "sf": Eagerly collected sf object (uses memory)

Can be set globally via ddbs_options(mode = "...") or per-function via this argument. Per-function overrides global setting.

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

Depends on the mode argument (or global preference set by ddbs_options):

  • duckspatial (default): A duckspatial_df (lazy spatial data frame) backed by dbplyr/DuckDB.

  • sf: An eagerly collected object in R memory, that will return the same data type as the sf equivalent (e.g. sf or units vector).

When name is provided, the result is also written as a table or view in DuckDB and the function returns TRUE (invisibly).

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

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

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

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

# store in duckdb
ddbs_write_table(conn, argentina_ddbs, "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)
} # }