dodgr.md

dodgr

Malcolm Morgan 2024-08-09

Load Inputs

Build graph

Get Routes

Extracting Origins and Destinations

origins <- lwgeom::st_startpoint(od_geo) |> st_as_sf()
origins <- st_coordinates(origins)


destinations <- lwgeom::st_endpoint(od_geo) |> st_as_sf()
destinations <- st_coordinates(destinations)

Routing

time_dodgr1 <- system.time({
  paths <- dodgr_paths(graph, origins, destinations, pairwise = TRUE)
})
time_dodgr1

##    user  system elapsed 
## 113.758   1.882 113.438

time_dodgr1[3]

## elapsed 
## 113.438

Helper function from UK2GTFS

path_to_sf <- function(dp, verts, simplify = FALSE) {
  # Check for emplyr paths
  if (length(dp[[1]]) > 0) {
    path <- verts[match(dp[[1]], verts$id), ]
    path <- matrix(c(path$x, path$y), ncol = 2)
    path <- sf::st_linestring(path)

    if (simplify) {
      path <- sf::st_as_sfc(list(path), crs = 4326)
      path <- sf::st_transform(path, 27700)
      path <- sf::st_simplify(path, 5, preserveTopology = TRUE)
      path <- sf::st_transform(path, 4326)
      path <- path[[1]]
    }
    return(path)
  } else {
    return(NA)
  }
}

paths_to_sf <- function(paths, verts) {
  dp.list <- purrr::map(paths, path_to_sf, verts = verts, .progress = TRUE)
  dp.list <- unname(dp.list)
  dp.list
}

verts <- dodgr_vertices(graph)
paths2 <- paths_to_sf(paths, verts)
paths2 <- sf::st_as_sfc(paths2, crs = 4326)

Plot

plot(paths2)

On contracted graph

v <- dodgr_vertices(graph)
o <- v$id[match_pts_to_verts(v, origins, connected = TRUE)]
d <- v$id[match_pts_to_verts(v, destinations, connected = TRUE)]
system.time({
  graphc <- dodgr_contract_graph(graph, verts=c(o, d))
})

##    user  system elapsed 
##  70.439   0.661  75.026

time_dodgr2 <- system.time({
  paths <- dodgr_paths(graphc, o, d, pairwise = TRUE)
})

Save times

timing_dodgr = data.frame(
  approach = "dodgr-no-contraction",
  version = as.character(packageVersion("dodgr")),
  date = Sys.Date(),
  time = round(time_dodgr1[3], 1)
)
# For second dodgr call:
timing_dodgr = rbind(timing_dodgr, data.frame(
  approach = "dodgr-contraction",
  version = as.character(packageVersion("dodgr")),
  date = Sys.Date(),
  time = round(time_dodgr2[3], 1)
))
# Save csv and append:
timings = readr::read_csv("timings.csv")

## Rows: 2 Columns: 3
## ── Column specification ────────────────────────────────────────────────────────
## Delimiter: ","
## chr  (2): approach, version
## date (1): date
## 
## ℹ Use `spec()` to retrieve the full column specification for this data.
## ℹ Specify the column types or set `show_col_types = FALSE` to quiet this message.

# Combine and deduplicate:
timings = bind_rows(timings, timing_dodgr) |>
  distinct(approach, version, date)
readr::write_csv(timings, "timings.csv")