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Create lines from point geometries

Source: R/ddbs_ops_unary.R
ddbs_make_line.Rd

Aggregates point geometries into a single LINESTRING by connecting them in their original order. Optionally, lines can be created per group using the by argument.

Usage

ddbs_make_line(
  x,
  by = NULL,
  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.

by

A character vector of column names to group by before aggregating points into lines. If NULL (default), all points are combined into a single line.

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

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).

Details

Connects input POINT geometries into a LINESTRING in row order (row 1 → row 2 → …). To control the connection order, sort the data beforehand with dplyr::arrange().

Examples

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

## read data
points_ddbs <- ddbs_open_dataset(
  system.file("spatial/points.gpkg", package = "duckspatial")
)

## create a single line from all points
ddbs_make_line(points_ddbs)

## create lines grouped by a column
ddbs_make_line(points_ddbs, by = "type")

## return as sf object
ddbs_make_line(points_ddbs, by = "type", mode = "sf")

## screate lines groupping by 2 columns
ddbs_make_line(points_ddbs, by = c("type", "class"))
} # }