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Merge line geometries into a single line

Source: R/ddbs_ops_unary_line.R
ddbs_line_merge.Rd

Merges a collection of line geometries that share endpoints into a single LINESTRING, or MULTILINESTRING if endpoints are not shared

Usage

ddbs_line_merge(
  x,
  preserve = TRUE,
  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.

preserve

a logical value. If TRUE (default), line direction is preserved

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).

Examples

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

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

## first, union by river name
rivers_union <- ddbs_union_agg(rivers_ddbs, by = "RIVER_NAME")

## merge lines, preserving direction
rivers_merged <- ddbs_line_merge(rivers_union)

## check Rio Eume (union doesn't guarantee the merging)
rivers_union |> filter(RIVER_NAME == "Rio Eume")
rivers_merged |> filter(RIVER_NAME == "Rio Eume")

} # }