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Creates a buffer around geometries

Source: R/ddbs_ops_unary.R
ddbs_buffer.Rd

Computes a polygon that represents all locations within a specified distance from the original geometry

Usage

ddbs_buffer(
  x,
  distance,
  num_triangles = 8L,
  cap_style = "CAP_ROUND",
  join_style = "JOIN_ROUND",
  mitre_limit = 1,
  conn = NULL,
  name = NULL,
  crs = NULL,
  crs_column = "crs_duckspatial",
  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.

distance

a numeric value specifying the buffer distance. Units correspond to the coordinate system of the geometry (e.g. degrees or meters)

num_triangles

an integer representing how many triangles will be produced to approximate a quarter circle. The larger the number, the smoother the resulting geometry. Default is 8.

cap_style

a character string specifying the cap style. Must be one of "CAP_ROUND" (default), "CAP_FLAT", or "CAP_SQUARE". Case-insensitive.

join_style

a character string specifying the join style. Must be one of "JOIN_ROUND" (default), "JOIN_MITRE", or "JOIN_BEVEL". Case-insensitive.

mitre_limit

a numeric value specifying the mitre limit ratio. Only applies when join_style is "JOIN_MITRE". It is the ratio of the distance from the corner to the mitre point to the corner radius. Default is 1.0.

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.

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).

Examples

if (FALSE) { # \dontrun{
## load package
library(duckspatial)

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

## read data
argentina_ddbs <- ddbs_open_dataset(
  system.file("spatial/argentina.geojson", 
  package = "duckspatial")
)

## store in duckdb
ddbs_write_vector(conn, argentina_ddbs, "argentina")

## basic buffer
ddbs_buffer(conn = conn, "argentina", distance = 1)

## buffer with custom parameters
ddbs_buffer(conn = conn, "argentina", distance = 1, 
            num_triangles = 16, cap_style = "CAP_SQUARE")

## buffer without using a connection
ddbs_buffer(argentina_ddbs, distance = 1)
} # }