3 Leaflet Karte

Teil der Aufgabenstellung war der Export einer mit Leaflet erstellten Karte mit geclusterten Punkten. Das Ergebnis dieses Kapitels wird für die Abgabe durch ein externes Script ausgeführt, das die Karte als HTML-Datei speichert.

library(tidyverse)
library(leaflet)
library(sf)

sf.data <-
  data |> 
  st_as_sf(coords = c("lng", "lat"), crs = "WGS84")

3.1 Basemap

bounds <- sf.regensburg |> st_bbox()

map <- 
  leaflet(
    options = leafletOptions(
      crs = leafletCRS(code = "WGS84"),
      preferCanvas = NULL
    )
  ) |> 
  addProviderTiles(
    provider = providers$OpenStreetMap.DE,
    group = "OSM",
    options = providerTileOptions(minZoom = 11)
  ) |> 
  setView(
    lng = (as.numeric(bounds[1]) + as.numeric(bounds[3]))/2,
    lat = (as.numeric(bounds[2]) + as.numeric(bounds[4]))/2,
    zoom = 12
  ) |> 
  setMaxBounds(
    lng1 = as.numeric(bounds[1] - 0.015), 
    lat1 = as.numeric(bounds[2] - 0.015), 
    lng2 = as.numeric(bounds[3] + 0.015), 
    lat2 = as.numeric(bounds[4] + 0.015)
  )

3.2 Marker

custom_popup <- function(data, header) {
  text <- 
    glue::glue(
      "<b>{header}</b> ",
      "<br>",
      "{data$month}/{data$year} ({data$hour} Uhr)"
    )
  return(text)
}

map <- 
  map |> 
  addAwesomeMarkers(
    data = data |> filter(severity == "Toedlich"),
    group = "Tödliche Unfälle",
    lng = ~lng,
    lat = ~lat,
    icon = awesomeIcons(
      icon = 'ios-close',
      iconColor = 'black',
      library = 'ion',
      markerColor = "red"
    ),
    clusterOptions = markerClusterOptions(),
    popup = custom_popup(
      data = data |> filter(severity == "Toedlich"), 
      header = "Tödlicher Unfall"
    )
  ) |> 
  addAwesomeMarkers(
    data = data |> filter(severity == "Schwer"),
    group = "Schwere Unfälle",
    lng = ~lng,
    lat = ~lat,
    icon = awesomeIcons(
      icon = 'ios-close',
      iconColor = 'black',
      library = 'ion',
      markerColor = "orange"
    ),
    clusterOptions = markerClusterOptions(),
    popup = custom_popup(
      data = data |> filter(severity == "Schwer"), 
      header = "Schwerer Unfall"
    )
  ) |> 
  addAwesomeMarkers(
    data = data |> filter(severity == "Leicht"),
    group = "Leichte Unfälle",
    lng = ~lng,
    lat = ~lat,
    icon = awesomeIcons(
      icon = 'ios-close',
      iconColor = 'black',
      library = 'ion',
      markerColor = "beige"
    ),
    clusterOptions = markerClusterOptions(),
    popup = custom_popup(
      data = data |> filter(severity == "Leicht"), 
      header = "Leichter Unfall"
    )
  )

3.3 Stadtteile als Shapefile

custom_label <- function(data) {
  text <- glue::glue(
    "{data$district}: {data$n} Unfälle"
  )
  return(text)
}

districts <-
  data |> 
  st_as_sf(coords = c("lng", "lat"), crs = "WGS84") |> 
  rename(
    points = geometry
  ) |> 
  st_join(
    y = sf.districts |> rename("district_shape" = geometry),
    join = st_within,
    left = TRUE
  ) |> 
  select(-m2) |> 
  as_tibble() |> 
  left_join(
    y = sf.districts |> rename("district_polygon" = geometry) ,
    by = "district"
  ) |>
  drop_na(district) |>
  mutate(
    district = as_factor(district) |>
      fct_infreq() |>
      fct_rev()
  ) |> 
  add_count(district) |> 
  select(district, district_polygon, n) |> 
  unique() |> 
  st_as_sf()

map <-
  map |> 
  addPolygons(
    data = districts,
    group = "Stadtteile",
    opacity = 1,
    weight = 0.5, 
    fillOpacity = 0.5,
    color = "black",
    fillColor = ~colorNumeric("viridis", n)(n),
    highlightOptions = highlightOptions(
      color = "white", 
      weight = 2,
      bringToFront = TRUE
    ),
    label = ~custom_label(data = districts)
  )

3.4 Bedienelemente

map <- 
  map |> 
    addProviderTiles(
      provider = providers$Stamen.TonerBackground,
      group = "Stadtteile",
      options = providerTileOptions(minZoom = 11)
    ) |> 
    addLayersControl(
      baseGroups = c("OSM", "Stadtteile"),
      overlayGroups = c("Tödliche Unfälle", "Schwere Unfälle", "Leichte Unfälle"),
      options = layersControlOptions(collapsed = FALSE)
    )

3.5 Finale Karte

map