cnt_path {centerline} | R Documentation |
Find the shortest path between start and end points within a polygon
Description
Find the shortest path between start and end points within a polygon
Usage
cnt_path(skeleton, start_point, end_point)
Arguments
skeleton |
an output from |
start_point |
one or more starting points. It should be of the same
class as the |
end_point |
one ending point of the same class as |
Details
The following function uses the sfnetworks::st_network_paths()
approach to
connect start_point
with end_point
by using the
skeleton
of a closed polygon as potential routes.
It is important to note that multiple starting points are permissible, but there can only be one ending point. Should there be two or more ending points, the algorithm will return an error.
Neither starting nor ending points are required to be located on the edges of a polygon (i.e., snapped to the boundary); they can be positioned wherever possible inside the polygon.
The algorithm identifies the closest nodes of the polygon's skeleton
to the starting and ending points and then connects them
using the shortest path possible along the skeleton.
Therefore, if more precise placement of start and end
points is necessary, consider executing the cnt_skeleton()
function with the keep = 1
option. In doing so, the resulting
skeleton may be more detailed, increasing the likelihood that the starting
and ending points are already situated on the skeleton paths.
Value
a list of sf
, sfc
, SpatVector
or geos_geometry
class objects of a LINESTRING
geometry
Examples
library(sf)
library(geos)
# Load Polygon and points data
polygon <-
sf::st_read(
system.file("extdata/example.gpkg", package = "centerline"),
layer = "polygon",
quiet = TRUE
) |>
geos::as_geos_geometry()
points <-
sf::st_read(
system.file("extdata/example.gpkg", package = "centerline"),
layer = "polygon_points",
quiet = TRUE
) |>
geos::as_geos_geometry()
# Find polygon's skeleton
pol_skeleton <- cnt_skeleton(polygon)
# Connect points
pol_path <-
cnt_path(
skeleton = pol_skeleton,
start_point = points[2],
end_point = points[1]
)
# Plot
plot(polygon)
plot(pol_skeleton, col = "blue", add = TRUE)
plot(points[1:2], col = "red", add = TRUE)
plot(pol_path, lwd = 3, add = TRUE)