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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), 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).

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"))
} # }