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Check geometry dimensions

Source: R/ddbs_dimensions.R
ddbs_has_dim.Rd

Functions to check whether geometries have Z (elevation) or M (measure) dimensions

Usage

ddbs_has_z(
  x,
  by_feature = TRUE,
  conn = NULL,
  name = NULL,
  new_column = "has_z",
  crs = NULL,
  crs_column = "crs_duckspatial",
  mode = NULL,
  overwrite = FALSE,
  quiet = FALSE
)

ddbs_has_m(
  x,
  by_feature = TRUE,
  conn = NULL,
  name = NULL,
  new_column = "has_m",
  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

new_column

Name of the new column to create on the input data. Ignored with mode = "sf".

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

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

  • mode = "sf": An eagerly collected vector in R memory.

  • When name is provided: writes the table in the DuckDB connection and returns TRUE (invisibly).

Details

These functions check for additional coordinate dimensions beyond X and Y:

  • ddbs_has_z() checks if a geometry has Z coordinates (elevation/altitude values). Geometries with Z dimension are often referred to as 3D geometries and have coordinates in the form (X, Y, Z).

  • ddbs_has_m() checks if a geometry has M coordinates (measure values). The M dimension typically represents a measurement along the geometry, such as distance or time, and results in coordinates of the form (X, Y, M) or (X, Y, Z, M).

Examples

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

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

## read data
countries_ddbs <- ddbs_open_dataset(
  system.file("spatial/countries.geojson", 
  package = "duckspatial")
) |> 
  filter(ISO3_CODE != "ATA")

## check if it has Z or M
ddbs_has_m(countries_ddbs)
ddbs_has_z(countries_ddbs)
} # }