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Force geometry dimensions

Source: R/ddbs_dimensions.R
ddbs_force_dim.Rd

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), no table is written and the result is returned as a duckspatial_df or sf object, depending on mode

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

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

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.

Examples

if (FALSE) { # \dontrun{
## 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)
} # }