Leaflet

1 Leaflet

Create interactive maps.
Note: You have to turn on your internet connection to see all maps.

1.1 Creating Map

Let’s create my first Leaflet MAP

library(leaflet)
my_map <- leaflet() %>%
  addTiles()
my_map

my_map2 <- leaflet()
my_map2 <- addTiles(my_map2)
my_map2

Data comes from Open Street Map.
This is just a background layer. We can add more things to this. Let’s try those.

1.2 Add Marker to Map

library(leaflet)
my_map <- my_map %>%
  addMarkers(lat = 7.8731, lng = 80.7718, popup = "Sri Lanka")
my_map

my_map2 <- addMarkers(map = my_map2, lat = 37.0902, lng = 95.7129, popup = "United States of America")
my_map2

Let’s try all these codes together.

my_place <- leaflet() %>%
  addTiles() %>%
  addMarkers(lat = 7.2549, lng = 80.5974, popup = "My University:)")
my_place

1.2.1 Adding lots of markers :)

set.seed(1234)    # 1234
df <- data.frame(lat = runif(20, min = 23.54, max = 58.21), 
                 lng = runif(20, min = 39.42, max = 86.32))
head(df)

##        lat      lng
## 1 27.48210 54.26912
## 2 45.11512 53.61632
## 3 44.66355 46.87926
## 4 45.15257 41.29581
## 5 53.38794 49.68170
## 6 45.73957 77.43707

df %>%
  leaflet() %>%
  addTiles() %>%
  addMarkers()

1.2.2 Adding custom markers

# Custom icons
uopIcon <- makeIcon(iconUrl = "https://www.pdn.ac.lk/commonfiles/imgs/crest.png",
                    iconWidth = 31*215/230, iconHeight = 31,
                    iconAnchorX = 31*215/230/2, iconAnchorY = 16)

# Marker locations
df <- data.frame(lat = c(7.2589, 7.2538, 7.2640, 7.2621, 7.2704), 
                 lng = c(80.5986, 80.5916, 80.5987, 80.5959, 80.6046))

# Custom popups
uopSite <- c(
  "<a href='http://sci.pdn.ac.lk/'>Faculty of Science</a>",
  "<a href='http://eng.pdn.ac.lk/'>Faculty of Engineering</a>",
  "<a href='http://med.pdn.ac.lk/'>Faculty of Medicine</a>",
  "<a href='http://agri.pdn.ac.lk/'>Faculty of Agriculture</a>",
  "<a href='http://dental.pdn.ac.lk/'>Faculty of Dental Science</a>")

df %>%
  leaflet() %>%
  addTiles() %>%
  addMarkers(icon = uopIcon, popup = uopSite)

1.3 Mapping clusters

set.seed(12500)    # 12500
df <- data.frame(lat = runif(500, min = 23.54, max = 58.21), 
                 lng = runif(500, min = 39.42, max = 86.32))
df %>%
  leaflet() %>%
  addTiles() %>%
  addMarkers(clusterOptions = markerClusterOptions())

1.4 Circular Markers

set.seed(1220)    # 1220
df <- data.frame(lat = runif(20, min = 23.54, max = 58.21), 
                 lng = runif(20, min = 39.42, max = 86.32))

df %>%
  leaflet() %>%
  addTiles() %>%
  addCircleMarkers() 

1.5 Draw shapes on Map

1.5.1 Circles

df <- data.frame(name = c("Sci", "eFac", "Medi", "Agri", "Denta"),
                 pop = c(2000, 2300, 1250, 1700, 970),
                 lat = c(7.2589, 7.2538, 7.2640, 7.2621, 7.2704), 
                 lng = c(80.5986, 80.5916, 80.5987, 80.5959, 80.6046))
# pop means population

df %>%
  leaflet() %>%
  addTiles() %>%
  addCircles(weight = 10, radius = sqrt(df$pop) * 10) 

## Assuming "lng" and "lat" are longitude and latitude, respectively

1.5.2 Rectangles

leaflet() %>%
  addTiles() %>%
  addRectangles(lat1 = 7.2589, lng1 = 80.5986, 
                lat2 = 7.2538, lng2 = 80.5916)

1.6 Adding Legends

df <- data.frame(lat = runif(20, min = 7.2589, max = 7.2704), 
                 lng = runif(20, min = 80.5916, max = 80.6046),
                 col = sample(c("red", "blue", "green"), 20, replace = TRUE),
                 stringsAsFactors = FALSE)

df %>%
  leaflet() %>%
  addTiles() %>%
  addCircleMarkers(color = df$col) %>%
  addLegend(labels = LETTERS[1:3], colors = c("blue", "red", "green"))

## Assuming "lng" and "lat" are longitude and latitude, respectively