Implement segmentation as part of the package

DESCRIPTION

@@ -13,12 +13,14 @@ Description: CRiSp (City River Spaces) provides tools to automate the
 License: Apache License (>= 2)
 URL: https://cityriverspaces.github.io/CRiSp/
 BugReports: https://github.com/CityRiverSpaces/crisp/issues
-Depends: 
+Depends:
     R (>= 2.10)
-Imports: 
+Imports:
+    dbscan,
     dplyr,
     lwgeom,
     osmdata,
+    rcoins,
     rlang,
     rstac,
     sf,
@@ -29,17 +31,19 @@ Imports:
     tibble,
     tidygraph,
     units
-Suggests: 
+Suggests:
     ggplot2,
     gridExtra,
     knitr,
     purrr,
     rmarkdown,
     testthat (>= 3.0.0)
-VignetteBuilder: 
+VignetteBuilder:
     knitr
 Config/testthat/edition: 3
 Encoding: UTF-8
 LazyData: true
 Roxygen: list(markdown = TRUE)
 RoxygenNote: 7.3.2
+Remotes:
+    github::CityRiverSpaces/rcoins

NAMESPACE

@@ -4,13 +4,12 @@ export(add_weights)
 export(as_bbox)
 export(as_network)
 export(clean_network)
-export(corridor)
 export(delineate_corridor)
 export(delineate_riverspace)
-export(delineate_segments)
 export(dem_to_cog)
 export(flatten_network)
 export(get_cd_char)
+export(get_corridor)
 export(get_cost_distance)
 export(get_dem)
 export(get_osm_bb)
@@ -19,6 +18,7 @@ export(get_osm_railways)
 export(get_osm_river)
 export(get_osm_streets)
 export(get_osmdata)
+export(get_segments)
 export(get_slope)
 export(get_stac_asset_urls)
 export(get_utm_zone)

R/corridor.R

@@ -14,7 +14,7 @@
 #'
 #' @return A simple feature geometry representing the river corridor
 #' @export
-corridor <- function(
+get_corridor <- function(
   network, river_centerline, river_surface, bbox, initial_method = "buffer",
   capping_method = "direct"
 ) {
@@ -133,11 +133,19 @@ split_aoi <- function(bbox, river) {
 #'
 #' @param geometry Geometry to split
 #' @param line Dividing (multi)linestring
+#' @param boundary Whether to return the split boundary instead of the regions
 #'
 #' @return A simple feature object
-split <- function(geometry, line) {
-  lwgeom::st_split(geometry, line) |>
+split <- function(geometry, line, boundary = FALSE) {
+  regions <- lwgeom::st_split(geometry, line) |>
     sf::st_collection_extract()
+  if (!boundary) {
+    return(regions)
+  } else {
+    boundaries <- sf::st_boundary(regions)
+    split_boundary <- sf::st_difference(boundaries, line)
+    return(split_boundary)
+  }
 }
 
 #' Identify the initial edges of the river corridor

R/delineate.R

@@ -11,15 +11,18 @@
 #' @param capping_method The method employed to connect the corridor edge end
 #'   points (i.e. to "cap" the corridor). See [cap_corridor()] for
 #'   the available methods
+#' @param angle_threshold Only network edges forming angles above this threshold
+#'   (in degrees) are considered when forming segment edges. See
+#'  `[get_segments()]`  and [strokes()]. Only used if `segments` is TRUE.
 #' @param segments Whether to carry out the corridor segmentation
 #' @param riverspace Whether to carry out the riverspace delineation
 #'
 #' @return A simple feature geometry
 #' @export
 delineate_corridor <- function(
   city_name, river_name, crs = NULL, bbox_buffer = NULL,
-  initial_method = "buffer", capping_method = "direct", segments = FALSE,
-  riverspace = FALSE
+  initial_method = "buffer", capping_method = "direct", angle_threshold = 90,
+  segments = FALSE, riverspace = FALSE
 ) {
   # Retrieve all relevant OSM datasets using the extended bounding box
   osm_data <- get_osmdata(city_name, river_name, crs, bbox_buffer)
@@ -32,25 +35,24 @@ delineate_corridor <- function(
   network <- as_network(network_edges)
 
   # Run the corridor delineation on the spatial network
-  corridor <- corridor(
+  corridor <- get_corridor(
     network, osm_data$river_centerline, osm_data$river_surface, bbox,
     initial_method, capping_method
   )
 
-  if (segments) delineate_segments()
+  if (segments) {
+    # Select the relevant part of the network
+    buffer_corridor <- 100  # TODO should this be an additional input parameter?
+    corridor_buffer <- sf::st_buffer(corridor, buffer_corridor)
+    network_filtered <- filter_network(network, corridor_buffer)
+
+    corridor <- get_segments(corridor, network_filtered,
+                             osm_data$river_centerline, angle_threshold)
+  }
   if (riverspace) delineate_riverspace()
   return(corridor)
 }
 
-
-#' Delineate segments of a river corridor.
-#'
-#' @return A simple feature geometry
-#' @export
-delineate_segments <- function() {
-  stop("Segmentation not yet implemented.")
-}
-
 #' Delinate the riverspace.
 #'
 #' @return A simple feature geometry

R/network.R

@@ -308,6 +308,26 @@ filter_network <- function(network, target) {
     tidygraph::filter(sfnetworks::node_intersects(target))
 }
 
-strokes <- function() {
-  stop("`strokes` not yet implemented.")
+#' Identify naturally continuos lines in a spatial network.
+#'
+#' Extend the specified network edges along the spatial network to form longer
+#' strokes. See [`rcoins::stroke()`] for more details.
+#'
+#' @param network A spatial network object
+#' @param from_edge The indices of the network edges to be continued
+#' @param angle_threshold Consecutive line segments are considered part of the
+#'   same continuous line if the internal angle they form is larger than
+#'   `angle_threshold`` (in degrees). Should be in the range [0, 180) degrees
+#' @param flow_mode If TRUE, line segments that belong to the same edge are not
+#'   split across strokes (even if they form internal angles smaller than
+#'  `angle_threshold`).
+#'
+#' @return Stroke geometries as a simple feature object
+strokes <- function(
+  network, from_edge, angle_threshold = 0., flow_mode = FALSE
+) {
+  rcoins::stroke(
+    network, angle_threshold = angle_threshold, attributes = FALSE,
+    flow_mode = flow_mode, from_edge = from_edge
+  )
 }