Skip to contents

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,
  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), no table is written and the result is returned as a duckspatial_df or sf object, depending on mode

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)
} # }