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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,
  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), 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.

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)
} # }