ddbs_force_dim: Force geometry dimensions

In duckspatial: R Interface to 'DuckDB' Database with Spatial Extension

Force geometry dimensions

Description

Functions to force geometries to have specific coordinate dimensions (X, Y, Z, M)

Usage

ddbs_force_2d(
  x,
  conn = NULL,
  name = NULL,
  mode = NULL,
  overwrite = FALSE,
  quiet = FALSE
)

ddbs_force_3d(
  x,
  var,
  dim = "z",
  conn = NULL,
  name = NULL,
  mode = NULL,
  overwrite = FALSE,
  quiet = FALSE
)

ddbs_force_4d(
  x,
  var_z,
  var_m,
  conn = NULL,
  name = NULL,
  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.
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
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.
var	A numeric variable in x to be converted in the dimension specified in the argument dim
dim	The dimension to add: either "z" (default) for elevation or "m" for measure values.
var_z	A numeric variable in x to be convered in Z dimension
var_m	A numeric variable in x to be convered in M dimension

Details

These functions modify the dimensionality of geometries:

• ddbs_force_2d() removes Z and M coordinates from geometries, returning only X and Y coordinates. This is useful for simplifying 3D or measured geometries to 2D.

• ddbs_force_3d() forces geometries to have three dimensions. When dim = "z" (default), adds or retains Z coordinates (X, Y, Z). When dim = "m", adds or retains M coordinates (X, Y, M). Missing values are typically set to 0. If the input geometry has a third dimension already, it will be replaced by the new one. If the input geometry has 4 dimensions, it will drop the dimension that wasn't specified.

• ddbs_force_4d() forces geometries to have all four dimensions (X, Y, Z, M). Missing Z or M values are typically set to 0.

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).

Examples

## Not run: 
## load packages
library(dplyr)
library(duckspatial)

## load data and add 2 numeric vars
countries_ddbs <- ddbs_open_dataset(
  system.file("spatial/countries.geojson", 
  package = "duckspatial")
) |> 
  dplyr::filter(ISO3_CODE != "ATA") |> 
  ddbs_area(new_column = "area") |> 
  ddbs_perimeter(new_column = "perim") 

## add a Z dimension
countries_z_ddbs <- ddbs_force_3d(countries_ddbs, "area")
ddbs_has_z(countries_z_ddbs)

## add a M dimension as 3D (removes current Z)
countries_m_ddbs <- ddbs_force_3d(countries_z_ddbs, "area", "m")
ddbs_has_z(countries_m_ddbs)
ddbs_has_m(countries_m_ddbs)

## add both Z and M
countries_zm_ddbs <- ddbs_force_4d(countries_ddbs, "area", "perim")
ddbs_has_z(countries_zm_ddbs)
ddbs_has_m(countries_zm_ddbs)

## drop both ZM
countries_drop_ddbs <- ddbs_force_2d(countries_zm_ddbs)
ddbs_has_z(countries_drop_ddbs)
ddbs_has_m(countries_drop_ddbs)

## End(Not run)

duckspatial documentation built on June 22, 2026, 9:08 a.m.