Skip to contents

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,
  new_column = "has_z",
  conn = NULL,
  name = NULL,
  mode = NULL,
  overwrite = FALSE,
  quiet = FALSE
)

ddbs_has_m(
  x,
  by_feature = TRUE,
  new_column = "has_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.

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.

new_column

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

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.

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 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)
} # }