✨ Add function to split linestring by points

NAMESPACE

@@ -4,7 +4,7 @@ S3method(extract_segmented_network_nodes,road_network)
 S3method(get_connected_links,road_network)
 S3method(plot,road_network)
 S3method(print,road_network)
-S3method(split_line,LINESTRING)
+S3method(split_linestring,LINESTRING)
 S3method(summary,road_network)
 export(bbox_to_polygon)
 export(create_bbox)
@@ -20,10 +20,10 @@ export(extract_segmented_network_nodes)
 export(filter_points_within_tolerance)
 export(generate_ids)
 export(get_connected_links)
-export(is_linestring_endpoint)
 export(osm_roads)
+export(remove_points_near_endpoints)
 export(sample_points_along_linestring)
-export(split_line)
+export(split_linestring)
 export(transform_to_cartesian)
 export(transform_to_geographic)
 importFrom(igraph,"E<-")
@@ -40,9 +40,11 @@ importFrom(sf,st_as_sf)
 importFrom(sf,st_boundary)
 importFrom(sf,st_cast)
 importFrom(sf,st_collection_extract)
+importFrom(sf,st_contains)
 importFrom(sf,st_coordinates)
 importFrom(sf,st_crop)
 importFrom(sf,st_crs)
+importFrom(sf,st_distance)
 importFrom(sf,st_equals)
 importFrom(sf,st_intersection)
 importFrom(sf,st_is_empty)

R/pavement-package.R

@@ -16,9 +16,11 @@
 #' @importFrom sf st_boundary
 #' @importFrom sf st_cast
 #' @importFrom sf st_collection_extract
+#' @importFrom sf st_contains
 #' @importFrom sf st_coordinates
 #' @importFrom sf st_crop
 #' @importFrom sf st_crs
+#' @importFrom sf st_distance
 #' @importFrom sf st_equals
 #' @importFrom sf st_intersection
 #' @importFrom sf st_is_empty

R/split-linestring.R

@@ -0,0 +1,88 @@
+#' Split a linestring into multiple segments
+#'
+#' @param linestring A linestring object.
+#' @param split_points A `sfc` object containing points to split the
+#'   linestring.
+#' @param tolerance A numeric value representing the maximum distance
+#'   allowed between the linestring and the split points. If the distance
+#'   between a split point and the linestring exceeds this value, the point
+#'   will not be used to split the linestring.
+#' @return A `sfc` object containing the split linestrings.
+#' @export
+#' @examples
+#' library(sf)
+#'
+#' # Create a linestring
+#' linestring <- create_linestring(0, -1, 0, 1, 2, 1, 2, 0, 0, 0)
+#'
+#' # Create a set of split points
+#' split_points <- st_sfc(
+#'   st_point(c(0, 0)),
+#'   st_point(c(1, 1)),
+#'   st_point(c(2, 0))
+#' )
+#'
+#' # Plot the linestring and split points
+#' plot(linestring)
+#' plot(split_points, add = TRUE)
+#'
+#' # Split the linestring
+#' segments <- split_linestring(linestring, split_points)
+#'
+#' # Plot the split linestrings
+#' plot(segments, col = c("#E69F00", "#56B4E9", "#009E73", "#F0E442"), lwd = 2)
+split_linestring <- function(linestring, split_points, tolerance = 0.01) {
+  UseMethod("split_linestring")
+}
+
+#' @export
+split_linestring.LINESTRING <- function(linestring,
+                                        split_points,
+                                        tolerance = 0.01) {
+  # Decompose the linestring into a list of line segments
+  line_segments <- decompose_linestring(linestring)
+
+  # Identify split points on the line segments, remove those
+  # near the endpoints, and add the start point of each line
+  points_on_lines <- lapply(line_segments, function(line_segment) {
+    valid_points <- filter_points_within_tolerance(
+      split_points,
+      line_segment,
+      tolerance
+    )
+    valid_points <- remove_points_near_endpoints(
+      valid_points,
+      line_segment,
+      tolerance
+    )
+    c(st_startpoint(line_segment), valid_points)
+  })
+
+  # Combine all split points and add the end point of the linestring
+  all_points <- st_sfc(c(
+    unlist(points_on_lines, recursive = FALSE),
+    st_endpoint(linestring)
+  ))
+
+  # Determine which points belong to each segment by calculating
+  # the segment index
+  is_split_point <- rep(FALSE, length(all_points))
+  is_split_point[unlist(st_contains(split_points, all_points))] <- TRUE
+  is_split_point[c(1, length(all_points))] <- FALSE
+  segment_index <- cumsum(is_split_point)
+
+  # Split the list of points into sub-lists based on the segment index
+  segment_points_list <- split(all_points, segment_index)
+  segment_points_list[-length(segment_points_list)] <- mapply(
+    c,
+    segment_points_list[-length(segment_points_list)],
+    lapply(all_points[is_split_point], st_sfc)
+  )
+
+  # Create linestring objects for each linestring segment
+  segments <- st_sfc(lapply(segment_points_list, function(segment_points) {
+    st_linestring(st_coordinates(segment_points))
+  }))
+
+  return(segments)
+}