duckspatial (version 0.9.0)

ddbs_length: Calculates the length of geometries

Description

Calculates the length of geometries from a DuckDB table or a sf object Returns the result as an sf object with a length column or creates a new table in the database. Note: Length units depend on the CRS of the input geometries (e.g., meters for projected CRS, or degrees for geographic CRS).

Usage

ddbs_length(
  x,
  conn = NULL,
  name = NULL,
  new_column = NULL,
  crs = NULL,
  crs_column = "crs_duckspatial",
  overwrite = FALSE,
  quiet = FALSE
)

Value

an sf object or TRUE (invisibly) for table creation

Arguments

x

An sf spatial object. Alternatively, it can be a string with the name of a table with geometry column within the DuckDB database 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

new_column

Name of the new column to create on the input data. If NULL, the function will return a vector with the result

crs

The coordinates reference system of the data. Specify if the data doesn't have a crs_column, and you know the CRS.

crs_column

a character string of length one specifying the column storing the CRS (created automatically by ddbs_write_vector). Set to NULL if absent.

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.

Examples

if (FALSE) {
## load packages
library(duckspatial)
library(sf)

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

## read data
rivers_sf <- st_read(system.file("spatial/rivers.geojson", package = "duckspatial"))

## store in duckdb
ddbs_write_vector(conn, rivers_sf, "rivers")

## calculate length (returns sf object with length column)
ddbs_length("rivers", conn)

## calculate length with custom column name
ddbs_length("rivers", conn, new_column = "length_meters")

## create a new table with length calculations
ddbs_length("rivers", conn, name = "rivers_with_length")

## calculate length in a sf object (without a connection)
ddbs_length(rivers_sf)
}