List of tiles

Let’s start with basic circle (default propose by leaflet). Please note that since we use here the addCircleMarkers() function, the size of the circle are set in pixels. It means that markers will keep always the same size, even when you zoom in or out!

See below in order to find how to change the size of the circle, dynamically or not.

#library
library(leaflet)
 
# Create 20 markers (Random points)
data = data.frame(
   long=sample(seq(-150,150),20),
   lat=sample(seq(-50,50),20),
   val=round(rnorm(20),2),
   name=paste("point",letters[1:20],sep="_")
) 
 
# Show a circle at each position
m = leaflet(data = data) %>%
   addTiles() %>%
   addCircleMarkers(~long, ~lat , popup = ~as.character(name))
m

# save the widget
# library(htmlwidgets)
# saveWidget(m, file="HtmlWidget/leaflet-182-add-circles.html", selfcontained = F)

Custom circles

It is possible to custom the circles. Really helpful since it permits to change it following the value of a variable from the dataset. Here, the size of the circle is defined by the val

# Create 20 markers (Random points)
data = data.frame(
   long=sample(seq(-150,150),20),
   lat=sample(seq(-50,50),20),
   val=round(rnorm(20),2),
   name=paste("point",letters[1:20],sep="_")
) 
 
# Show a CUSTOM circle at each position. Size defined in Pixel. Size does not change when you zoom
m=leaflet(data = data) %>%
   addTiles() %>%
   addCircleMarkers(
      ~long, ~lat, 
      radius=~val*14 , 
      color=~ifelse(data$val>0 , "red", "orange"),
      stroke = TRUE, 
      fillOpacity = 0.2,
      popup = ~as.character(name)
   ) 
m

# save the widget
# library(htmlwidgets)
# saveWidget(m, file="HtmlWidget/leaflet-182-add-circles-2.html", selfcontained = F)

Custom circles with size that change when you zoom

You can also add circles with the addCircle() function. This time, the radius of the circle is defined in meters. It means that its size will change when you zoom on the map!

#library
library(leaflet)
 
# Create 20 markers (Random points)
data = data.frame(
   long=sample(seq(-150,150),20),
   lat=sample(seq(-50,50),20),
   val=round(rnorm(20),2),
   name=paste("point",letters[1:20],sep="_")
) 
 
# Show a CUSTOM circle at each position. Size in meters --> change when you zoom.
m = leaflet(data = data) %>%
   addTiles() %>%
   addCircles(
      ~long, ~lat, 
      radius=~val*1000000 , 
      color=~ifelse(data$val>0 , "red", "orange"),
      stroke = TRUE, 
      fillOpacity = 0.2,
      popup = ~as.character(name)
   ) %>% 
  setView(lng = 166.45, lat = 21, zoom = 2)
m

# save the widget
# library(htmlwidgets)
# saveWidget(m, file="HtmlWidget/leaflet-182-add-circles-3.html", selfcontained = F)

Add rectangles

Lastly, how to add a rectangle with the addRectangles() function. You have to give the 2 coordinates of 2 opposites corners of the rectangle.

#library
library(leaflet)
 
# Create 20 markers (Random points)
data = data.frame(
   long=sample(seq(-150,150),20),
   lat=sample(seq(-50,50),20),
   val=round(rnorm(20),2),
   name=paste("point",letters[1:20],sep="_")
) 
 
# Show a rectangle
m = leaflet() %>% addTiles() %>%  
  addRectangles(
    lng1=-118.456554, lat1=34.078039,
    lng2=-118.436383, lat2=34.062717,
    fillColor = "transparent"
  )
m

# save the widget
# library(htmlwidgets)
# saveWidget(m, file="HtmlWidget/leaflet-182-add-rectangles.html", selfcontained = F)

Going further

You might be interested in how to change the tile style and the map section of the leaflet map.

Change and customize circles and rectangles on a leaflet map

List of tiles

Custom circles

Custom circles with size that change when you zoom

Add rectangles

Going further

❤️ 10 best R tricks ❤️