From 36952ff52159eaa39754aba20bf5361606b84b9c Mon Sep 17 00:00:00 2001
From: robinlovelace <rob00x@gmail.com>
Date: Mon, 23 Sep 2019 12:00:57 +0100
Subject: [PATCH] Close #237

---
 vignettes/stplanr-route-nets.Rmd | 52 +++++++++++++++++++++++++++++++-
 1 file changed, 51 insertions(+), 1 deletion(-)

diff --git a/vignettes/stplanr-route-nets.Rmd b/vignettes/stplanr-route-nets.Rmd
index 8e3f5994..e1ea67eb 100644
--- a/vignettes/stplanr-route-nets.Rmd
+++ b/vignettes/stplanr-route-nets.Rmd
@@ -63,18 +63,27 @@ class(sln@nb); length(unique(unlist(sln@nb)))
 identical(sln@sl$geometry, rnet$geometry)
 ```
 
+```{r}
+sln_nodes = sln2points(sln)
+nrow(sln_nodes)
+length(sln@nb)
+```
+
 ```{r}
 rnet_coordinates = sf::st_coordinates(rnet)
 set.seed(85)
 x = runif(n = 2, min = min(rnet_coordinates[, 1]), max = max(rnet_coordinates[, 1]))
 y = runif(n = 2, min = min(rnet_coordinates[, 2]), max = max(rnet_coordinates[, 2]))
-xy_sf = sf::st_as_sf(data.frame(n = 1:2, x, y), coords = c("x", "y"), crs = sf::st_crs(rnet))
+crs = sf::st_crs(rnet)
+xy_sf = sf::st_as_sf(data.frame(n = 1:2, x, y), coords = c("x", "y"), crs = crs)
 xy_nodes = stplanr::find_network_nodes(sln = sln, x = x, y = y)
 ```
 
 # Routing on route networks
 
 ```{r}
+plot(rnet$geometry)
+plot(sln_nodes, add = TRUE)
 xy_path = sum_network_routes(sln = sln, start = xy_nodes[1], end = xy_nodes[2], sumvars = "length")
 # xy_path = sum_network_links(sln = sln, start = xy_nodes[1], end = xy_nodes[2])
 plot(rnet$geometry)
@@ -82,6 +91,47 @@ plot(xy_sf$geometry, add = TRUE)
 plot(xy_path$geometry, add = TRUE, lwd = 5)
 ```
 
+# Adding new nodes
+
+New nodes can be added to the network, although this should be done before the graph representation is created.
+Imagine we want to create a point half way along the the most westerly route segment in the network, near the coordinates -1.540, 53.826:
+
+```{r netpoint}
+new_point_coordinates = c(-1.540, 53.826)
+p = sf::st_sf(geometry = sf::st_sfc(sf::st_point(new_point_coordinates)), crs = crs)
+```
+
+We can identify the nearest point on the network at this point and use that to split the associated linestring:
+
+```{r, fig.show='hold'}
+pmat = matrix(new_point_coordinates, ncol = 2)
+rmat = nabor::knn(data = rnet_coordinates[, 1:2], query = pmat, k = 1)
+rnet_point_nearst_p = sf::st_sfc(sf::st_point(rnet_coordinates[rmat$nn.idx, 1:2]), crs = crs)
+rnet_intersecting_p = lengths(st_intersects(rnet, rnet_point_nearst_p)) > 0
+rnet_line_near_p = rnet[rnet_intersecting_p, ]
+rnet_lines_far_p = rnet[!rnet_intersecting_p, ]
+rnet_new_geometry_collection = lwgeom::st_split(rnet_line_near_p, rnet_point_nearst_p)
+rnet_new_linestrings = sf::st_cast(rnet_new_geometry_collection)
+rnet_new = rbind(rnet_lines_far_p, rnet_new_linestrings)
+plot(rnet_lines_far_p$geometry)
+plot(rnet_line_near_p$geometry, col = "grey", lwd = 6, add = TRUE)
+plot(rnet_new_linestrings, col = "blue", lwd = c(1, 4), add = TRUE)
+sln_new = SpatialLinesNetwork(rnet_new)
+node_new = find_network_nodes(sln = sln_new, x = new_point_coordinates[1], y = new_point_coordinates[2])
+node_xy2 = find_network_nodes(sln = sln_new, x = x[1], y = y[1])
+sln_new_path = sum_network_routes(sln = sln_new, start = node_new[1], end = node_xy2, sumvars = "length")
+plot(rnet_new$geometry)
+plot(sln_nodes$geometry, col = "red", add = TRUE)
+plot(p$geometry, cex = 5, add = TRUE)
+plot(sln_new_path$geometry, lwd = 5, add = TRUE)
+```
+
+
+
+```{r newnetplot}
+
+```
+
 # Other approaches
 
 Other approaches to working with route networks include: