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In Part 1 and Part 2 of this series, we scraped plane crash data from the web and complemented it with the geocoordinates of departure, crash and intended arrival location. In this third part, we will visualise the data on a map using the leaflet package.

<pre class="r"><code>library("leaflet") library("geosphere")</code>

Again we keep only complete rows of the data:

<pre class="r"><code>data <- data[complete.cases(data), ]</code>

Let us first prepare a color palette with three different shades of red. We will need it later on.

<pre class="r"><code>pal <- colorNumeric(palette = c("#ffe6e6", "#ff8080", "#ff0000"),                     domain = c(0, 100))</code>

In order to visualise the flight route between departure and destination, we create geocoordinates of the way in between. This can be done with the function gcIntermediate from the geosphere package. To decide how many points we should create, we first need a measure of the distance between the two locations. The higher the distance, the more dots we will need for the visualisation.

<pre class="r"><code># distance between from and to location  data %<>% mutate(dist = abs(latFrom - latTo) + abs(lngFrom - lngTo)) # create many geocoordinates between "from" and "to"  geoLines <- lapply(seq(nrow(data)),                    function(i) {                      gcIntermediate(c(data$lngFrom[i], data$latFrom[i]),                                     c(data$lngTo[i], data$latTo[i]),                                     n = 10 * data$dist[i], addStartEnd = TRUE, breakAtDateLine = TRUE) %>% as.data.frame %>% setNames(c("lng", "lat")) }) %>% bind_rows }</code> Now everything is ready to create a map with the leaflet function: <pre class="r"><code># empty plot leaflet(data, width = "100%") %>% # add map addProviderTiles("CartoDB.DarkMatterNoLabels") %>% # change displayed section setView(10, 35, zoom = 2) %>% # add flight routes addCircles(lng = geoLines$lng,              lat = geoLines\$lat,              col = "#6E6E6E",              radius = 1,              opacity = .05,              weight = 1) %>%       # add a slightly larger dot for the departure location   addCircleMarkers(~lngFrom,                    ~latFrom,                    color = "#6E6E6E",                    radius = 1,                    opacity = 0.8) %>%       # mark crash locations; the color reflects the share of victims   addCircleMarkers(~lngCrashLoc,                    ~latCrashLoc,                    color = ~pal(deathRate),                    radius = 3)</code>

Further parts of the Plane Crash series: