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Convert point geometries to QuadKey tiles

Source: R/ddbs_quadkey.R
ddbs_quadkey.Rd

Transforms point geometries into QuadKey identifiers at a specified zoom level, a hierarchical spatial indexing system used by mapping services.

Usage

ddbs_quadkey(
  x,
  level = 10,
  field = NULL,
  fun = "mean",
  background = NA,
  conn = NULL,
  name = NULL,
  crs = NULL,
  crs_column = "crs_duckspatial",
  output = "polygon",
  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.

level

An integer specifying the zoom level for QuadKey generation (1-23). Higher values provide finer spatial resolution. Default is 10.

field

Character string specifying the field name for aggregation.

fun

aggregation function for when there are multiple quadkeys (e.g. "mean", "min", "max", "sum").

background

numeric. Default value in raster cells without values. Only used when output = "raster"

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

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

crs_column

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

output

Character string specifying output format. One of:

  • "polygon" - Returns QuadKey tile boundaries as duckspatial_df (default)

  • "raster" - Returns QuadKey values as a SpatRaster

  • "tilexy" - Returns tile XY coordinates as a tibble

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 output argument

  • polygon (default): A lazy spatial data frame backed by dbplyr/DuckDB.

  • raster: An eagerly collected SpatRaster object in R memory.

  • tilexy: An eagerly collected tibble without geometry in R memory.

When name is provided, the result is also written as a table or view in DuckDB and the function returns TRUE (invisibly).

Details

QuadKeys divide the world into a hierarchical grid of tiles, where each tile is subdivided into four smaller tiles at the next zoom level. This function wraps DuckDB's ST_QuadKey spatial function to generate these tiles from input geometries.

Note that creating a table inside the connection will generate a non-spatial table, and therefore, it cannot be read with ddbs_read_vector().

Examples

if (FALSE) { # \dontrun{
## load packages
library(duckspatial)
library(sf)
library(terra)

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

## create random points in Argentina
argentina_sf <- st_read(system.file("spatial/argentina.geojson", package = "duckspatial"))
rand_sf <- st_sample(argentina_sf, 100) |> st_as_sf()
rand_sf["var"] <- runif(100)

## store in duckdb
ddbs_write_vector(conn, rand_sf, "rand_sf")

## generate QuadKey polygons at zoom level 8
qkey_ddbs <- ddbs_quadkey(conn = conn, "rand_sf", level = 8, output = "polygon")

## generate QuadKey raster with custom field name
qkey_rast <- ddbs_quadkey(conn = conn, "rand_sf", level = 6, output = "raster", field = "var")

## generate Quadkey XY tiles
qkey_tiles_tbl <- ddbs_quadkey(conn = conn, "rand_sf", level = 10, output = "tilexy")
} # }