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,
  crs = NULL,
  crs_column = "crs_duckspatial",
  area_column = "area",
  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

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.

area_column

Character string specifying the name of the output area column. Default is "area".

overwrite

Boolean. whether to overwrite the existing table if it exists. Defaults to FALSE. This argument is ignore when name is NULL.

quiet

A logical value. If TRUE, suppresses any informational messages. Defaults to FALSE.

Value

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)
#> ✔ 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
#> 1      AR Argentina       ARG Argentina  AR 2021-01-01 4.253708e+12
#>                         geometry
#> 1 POLYGON ((-6973632 -2541624...

## calculate area with custom column name
ddbs_area("argentina", conn, area_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")
#> ✔ Query successful

## calculate area in a sf object
ddbs_area(argentina_sf)
#> ✔ 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
#> 1      AR Argentina       ARG Argentina  AR 2021-01-01 4.253708e+12
#>                         geometry
#> 1 POLYGON ((-6973632 -2541624...