Calculates the area of geometries

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

Usage

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

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.

Value

a vector, an sf object or TRUE (invisibly) for table creation

Examples

## load packages
library(duckdb)
#> Loading required package: DBI
library(duckspatial)
library(sf)
#> Linking to GEOS 3.12.1, GDAL 3.8.4, PROJ 9.4.0; sf_use_s2() is TRUE

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

## read data
argentina_sf <- st_read(system.file("spatial/argentina.geojson", package = "duckspatial")) |> 
    st_transform("EPSG:3857")
#> Reading layer `argentina' from data source 
#>   `/home/runner/work/_temp/Library/duckspatial/spatial/argentina.geojson' 
#>   using driver `GeoJSON'
#> Simple feature collection with 1 feature and 6 fields
#> Geometry type: POLYGON
#> Dimension:     XY
#> Bounding box:  xmin: -73.52455 ymin: -52.39755 xmax: -53.62409 ymax: -21.81793
#> Geodetic CRS:  WGS 84

## store in duckdb
ddbs_write_vector(conn, argentina_sf, "argentina")
#> ✔ Table argentina successfully imported

## calculate area (returns sf object with area column)
ddbs_area("argentina", conn)
#> [1] 4.253708e+12

## calculate area with custom column name
ddbs_area("argentina", conn, new_column = "area_sqm")
#> ✔ Query successful
#> Simple feature collection with 1 feature and 7 fields
#> Geometry type: POLYGON
#> Dimension:     XY
#> Bounding box:  xmin: -8184715 ymin: -6872329 xmax: -5969406 ymax: -2489680
#> Projected CRS: WGS 84 / Pseudo-Mercator
#>   CNTR_ID NAME_ENGL ISO3_CODE CNTR_NAME FID       date     area_sqm
#> 1      AR Argentina       ARG Argentina  AR 2021-01-01 4.253708e+12
#>                         geometry
#> 1 POLYGON ((-6973632 -2541624...

## create a new table with area calculations
ddbs_area("argentina", conn, name = "argentina_with_area")
#> [1] 4.253708e+12

## calculate area in a sf object
ddbs_area(argentina_sf)
#> [1] 4.253708e+12