Add functions to split routes and add nodes route networks

[Robinlovelace]

Emerging from #237 (comment), suggestion from @rafapereirabr

[Robinlovelace]

It's worth splitting the line splitting and node adding components into different functions.

[Robinlovelace]

Now implemented in the rnet-add-node branch and works as follows:

remotes::install_github("ropensci/stplanr", "rnet-add-node")
#> Skipping install of 'stplanr' from a github remote, the SHA1 (d5e0b0a3) has not changed since last install.
#>   Use `force = TRUE` to force installation
library(stplanr)
#> Registered S3 method overwritten by 'R.oo':
#>   method        from       
#>   throw.default R.methodsS3
sample_routes = routes_fast_sf[2:6, NULL]
sample_routes$value = rep(1:3, length.out = 5)
rnet = overline2(sample_routes, attrib = "value")
#> 2019-09-24 09:37:14 constructing segments
#> 2019-09-24 09:37:14 building geometry
#> 2019-09-24 09:37:14 simplifying geometry
#> 2019-09-24 09:37:14 aggregating flows
#> 2019-09-24 09:37:14 rejoining segments into linestrings
sln = SpatialLinesNetwork(rnet)
#> Linking to GEOS 3.7.1, GDAL 2.4.2, PROJ 5.2.0
p = sf::st_sfc(sf::st_point(c(-1.540, 53.826)), crs = sf::st_crs(rnet))
sln_nodes = sln2points(sln)
sln_new = sln_add_node(sln, p)
#> although coordinates are longitude/latitude, st_nearest_feature assumes that they are planar
route = route_local(sln_new, p, sln_nodes[9, ])
plot(sln)
plot(sln_nodes, pch = as.character(1:nrow(sln_nodes)), add = TRUE)
plot(route$geometry, lwd = 9, add = TRUE)

^{Created on 2019-09-24 by the reprex package (v0.3.0)}

Work for you @rafapereirabr? Any feedback welcome.

[Robinlovelace]

Note that sln_add_node was the most concise yet clear name I could come up with. And based on the principle of modularity, I've not implemented it as a megafunction but a small family of related functions that could be useful in their own right. See here for the source code - comment on that very welcome. Heads-up @mpadge, @agila5, @richardellison: https:/ropensci/stplanr/blob/rnet-add-node/R/route-add-node.R

[mpadge]

Great stuff. This functionality should come relatively soon into dodgr, and that is definitely a strong benchmark. Nice work

[rafapereirabr]

This works like a charm. Thanks Robin !

[rafapereirabr]

And please feel free to add an answer to that SO question:

library(stplanr)

# add node to network
 sln_new <- sln_add_node(sln = sln, p = p)

# identify nodes
 sln_nodes = sln2points(sln_new)

# route new node to any other node in the newtork
  route_new <- route_local(sln = sln_new, from = p, to = sln_nodes[15, ])

# plot results
  plot(sln_new)
  plot(p, add = TRUE)
  plot(route_new, lwd = 5, add = TRUE)