Playing with the Leaflet package

Author

Arvind V.

Published

May 13, 2017

Modified

October 11, 2025

1 Introduction

This Tutorial works through the ideas at Leaflet.

Leaflet

Leaflet is a JavaScript library for creating dynamic maps that support panning and zooming along with various annotations like markers, polygons, and popups.

In this tutorial we will work only with vector data. In a second part, we will work with raster data in leaflet. (Hah! When??)

2 Setting up R Packages

library(tidyverse)
library(leaflet)
library(leaflet.extras)
library(leaflet.providers)

# Data
library(osmdata) # Import OSM Vector Data into R

# devtools::install_github("datadotworld/data.world-r", build_vignettes = TRUE)
library(data.world)

3 Basic Features of a leaflet Map

Show the Code

m <- leaflet() %>%
  # Add default OpenStreetMap map tiles
  addTiles() %>%
  # Set view to be roughly centred on Bangalore City
  setView(lng = 77.580643, lat = 12.972442, zoom = 12)

m

Figure 1: Basic Map with leaflet

Click on the map to zoom in; Shift+Click to zoom out. leaflet by default uses Open Street Map as its base map. We can use other base maps too, as we will see later.

4 Add Shapes to a Map

leaflet offers several commands to add points, popups, markers, icons, lines, polylines, and polygons to a map. Let us examine a few of these.

Adding Shapes

What are the different commands in leaflet that enable us to add shapes to a map?

and a good few more!!

4.1 Add Markers with popups

Show the Code

m %>% addMarkers(
  lng = 77.580643, lat = 12.972442,
  popup = "The birthplace of Rvind"
)

Figure 2: Basic Map with Markers

This uses the default pin shape as the Marker. Click on the Marker for the popup to appear.

4.2 Adding Popups to a Map

Popups are small boxes containing arbitrary HTML, that point to a specific point on the map. Use the addPopups() function to add standalone popup to the map.

Show the Code

m %>%
  addPopups(
    lng = 77.580643,
    lat = 12.972442,
    popup = paste(
      "The birthplace of Rvind",
      "<br>",
      "Website: <a href = https://arvindvenkatadri.com>Arvind V's Website </a>",
      "<br>"
    ),
    ## Ensuring we cannot close the popup,
    ## else we will not be able to find where it is,
    ## since there is no Marker

    options = popupOptions(closeButton = FALSE)
  )

Figure 3: Basic Map with Popups

Popups are usually added to icons, Markers and other shapes can show up when these are clicked.

4.3 Adding Labels to a Map

Labels are messages attached to all shapes, using the argument label wherever it is available.

Labels are static, and Popups are usually visible on mouse click.

Hence a Marker can have both a label and a popup. For example, the function addPopup() offers only a popup argument, whereas the function addMarkers() offers both a popup and a label argument.

It is also possible to create labels standalone using addLabelOnlyMarkers() where we can show only text and no Markers.

Show the Code

m %>%
  addMarkers(
    lng = 77.580643,
    lat = 12.972442,

    # Here is the Label defn.
    label = "The birthplace of Rvind",
    labelOptions = labelOptions(
      noHide = TRUE, # Label always visible
      textOnly = F,
      textsize = 20
    ),

    # And here is the popup defn.
    popup = paste(
      "PopUp Text: <a href = https://arvindvenkatadri.com>Arvind V's Website </a>",
      "<br>"
    )
  )

Figure 4: Basic Map with Labels

4.4 Adding Circles and CircleMarkers on a Map

We can add shapes on to a map to depict areas or locations of interest.

addCircles and addCircleMarkers

The radius argument works differently in addCircles() and addCircleMarkers().

Show the Code

# Some Cities in the US and their location
md_cities <- tibble(
  name = c("Baltimore", "Frederick", "Rockville", "Gaithersburg", "Bowie", "Hagerstown", "Annapolis", "College Park", "Salisbury", "Laurel"),
  pop = c(619493, 66169, 62334, 61045, 55232, 39890, 38880, 30587, 30484, 25346),
  lat = c(39.2920592, 39.4143921, 39.0840, 39.1434, 39.0068, 39.6418, 38.9784, 38.9897, 38.3607, 39.0993),
  lng = c(-76.6077852, -77.4204875, -77.1528, -77.2014, -76.7791, -77.7200, -76.4922, -76.9378, -75.5994, -76.8483)
)


md_cities %>%
  leaflet() %>%
  addTiles() %>%
  # CircleMarkers, in blue
  # radius scales the Marker. Units are in Pixels!!
  # Here, radius is made proportional to `pop` number
  addCircleMarkers(
    radius = ~ pop / 1000, # Pixels!!
    color = "blue",
    stroke = FALSE, # no border for the Markers
    opacity = 0.8
  ) %>%
  # Circles, in red
  addCircles(
    radius = 5000, # Meters !!!
    stroke = TRUE,
    color = "yellow", # Stroke Colour
    weight = 3, # Stroke Weight
    fill = TRUE,
    fillColor = "red",
  )

Figure 5: Basic Map with Circles

The shapes need not be of fixed size or colour; their attributes can be made to correspond to other attribute variables in the geospatial data, as we did with radius in the addCircleMarkers() function above.

4.5 Adding Rectangles to a Map

Show the Code

## Adding Rectangles
leaflet() %>%
  addTiles() %>%
  setView(lng = 77.580643, lat = 12.972442, zoom = 6) %>%
  addRectangles(
    lat1 = 10.3858, lng1 = 75.0595,
    lat2 = 12.8890, lng2 = 77.9625
  )

Figure 6: Basic Map with Rectangles

4.6 Add Polygons to a Map

Show the Code

## Adding Polygons
leaflet() %>%
  addTiles() %>%
  setView(lng = 77.580643, lat = 12.972442, zoom = 6) %>%
  # arbitrary vector data for lat and lng
  # This is almost like WKT
  addPolygons(
    lng = c(73.5, 75.9, 76.1, 77.23, 79.8),
    lat = c(10.12, 11.04, 11.87, 12.04, 10.7)
  )

Figure 7: Basic Map with Polygons

4.7 Add PolyLines to a Map

This can be useful say for manually marking a route on a map, with waypoints.

Show the Code

leaflet() %>%
  addTiles() %>%
  setView(lng = 77.580643, lat = 12.972442, zoom = 6) %>%
  # arbitrary vector data for lat and lng
  # If start and end points are the same, it looks like Polygon
  # Without the fill
  # Two Vectors
  addPolylines(
    lng = c(73.5, 75.9, 76.1, 77.23, 79.8),
    lat = c(10.12, 11.04, 11.87, 12.04, 10.7)
  ) %>%
  # Add Waypoint Icons
  # Same Two Vectors
  addMarkers(
    lng = c(73.5, 75.9, 76.1, 77.23, 79.8),
    lat = c(10.12, 11.04, 11.87, 12.04, 10.7)
  )

Figure 8: Basic Map with PolyLines

As seen, we have created Markers, Labels, Polygons, and PolyLines using fixed.i.e. literal text and numbers. In the following we will also see how external geospatial data columns can be used instead of these literals.

The mapedit package

https://r-spatial.org//r/2017/01/30/mapedit_intro.html can also be used to interactively add shapes onto a map and save as an geo-spatial object.

5 Using `leaflet` with External Geospatial Data

On to something more complex. We want to plot an external user-defined set of locations on a leaflet map. leaflet takes in geographical data in many ways and we will explore most of them. We know of course, that external data can be of different geometries: POINT/MULTIPOINT; LINE/MULTILINE; POLYGON/MULTIPOLYGON and so on.

5.1 POINT Data Sources for `leaflet`

Point data for markers can come from a variety of sources:

Vectors: Simply provide numeric vectors as lng and lat arguments, which we have covered already in the preceding sections.
Matrices: Two-column numeric matrices (first column is longitude, second is latitude)
Data Frames: Data frame/tibble with latitude and longitude columns. You can explicitly tell the marker function which columns contain the coordinate data (e.g. addMarkers(lng = ~Longitude, lat = ~Latitude)), or let the function look for columns named lat/latitude and lon/lng/long/longitude (case insensitive).
Package sf: POINT,sfc_POINT, and sf objects (from thesf package); only X and Y dimensions will be considered
Package sp: SpatialPoints or SpatialPointsDataFrame objects (from the sp package)

Not using sp

We will not consider the use of sp related data structures for plotting POINTs in leaflet since sp is being phased out in favour of the more modern package sf.

Points using Two-Column Matrices

We can first quickly try providing lon and lat info in a two column matrix. This can be useful to plot a bunch of points recorded on a mobile phone app, for example.

Show the Code

mysore5 <- matrix(
  c(
    runif(5, 76.652985 - 0.01, 76.652985 + 0.01),
    runif(5, 12.311827 - 0.01, 12.311827 + 0.01)
  ),
  nrow = 5
)
mysore5

         [,1]     [,2]
[1,] 76.65736 12.31561
[2,] 76.64435 12.31723
[3,] 76.65732 12.31397
[4,] 76.65691 12.31166
[5,] 76.64535 12.31743

Show the Code

leaflet(data = mysore5) %>%
  addProviderTiles(providers$OpenStreetMap) %>%
  # Pick an icon from <https://www.w3schools.com/bootstrap/bootstrap_ref_comp_glyphs.asp>
  addAwesomeMarkers(
    icon = awesomeIcons(
      icon = "music",
      iconColor = "black",
      library = "fa"
    ),
    popup = "Carnatic Music !!"
  )

Figure 9: Plotting Points from a 2-Column Matrix

Points using simple Data Frames

Let us read in the data set from data.world that gives us POINT locations of all airports in India in a data frame / tibble. The dataset is available at https://query.data.world/s/ahtyvnm2ybylf65syp4rsb5tulxe6a and, for poor peasants especially, also by clicking the download button here below. Save it in a convenient data folder in your project and read it in.

Using data.world

You will need the package data.world and also need to register your credentials for that page with RStudio. The (simple!) instructions are available here at data.world.

Show the Code

# library(devtools)
# devtools::install_github("datadotworld/data.world-r", build_vignettes = TRUE)

library(data.world)

india_airports <-
  read_csv("https://query.data.world/s/ahtyvnm2ybylf65syp4rsb5tulxe6a") %>%
  slice(-1) %>% # Drop the first row which contains labels
  dplyr::mutate(
    id = as.integer(id),
    latitude_deg = as.numeric(latitude_deg),
    longitude_deg = as.numeric(longitude_deg),
    elevation_ft = as.integer(elevation_ft)
  ) %>%
  rename("lon" = longitude_deg, "lat" = latitude_deg) %>%
  # Remove four locations which seem to be in the African Atlantic
  filter(!id %in% c(330834, 330867, 325010, 331083))

india_airports %>% head()

Here is the data:

Let us plot this in leaflet, using an ESRI National Geographic style map instead of the default OSM Base Map. We will also place small circle markers for each airport.

Show the Code

leaflet(data = india_airports) %>%
  setView(lat = 18, lng = 77, zoom = 4) %>%
  # Add NatGeo style base map
  addProviderTiles(providers$Esri.NatGeoWorldMap) %>% # ESRI Basemap

  # Add Markers for each airport
  addCircleMarkers(
    lng = ~lon, lat = ~lat,
    # Optional, variables stated for clarity
    # leaflet can automatically detect lon-lat columns
    # if they are appropriately named in the data
    # longitude/lon/lng
    # latitude/lat
    radius = 2, # Pixels
    color = "red",
    opacity = 1
  )

Figure 10: Plotting Airports Tibble Data from data.world

We can also change the icon for each airport. leaflet allows the use of ionicons, glyphicons, and FontAwesomeIcons.

Here is the IATA icon: download and save it and make sure this code below has the proper path to this .png file!

Figure 11: IATA Logo

Show the Code

# Define popup message for each airport
# Based on data in india_airports
popup <- paste(
  "<strong>",
  india_airports$name,
  "</strong><br>",
  india_airports$iata_code,
  "<br>",
  india_airports$municipality,
  "<br>",
  "Elevation(feet)",
  india_airports$elevation_ft,
  "<br>",
  india_airports$wikipedia_link,
  "<br>"
)

iata_icon <- makeIcon(
  "../../images/iata-logo-transp.png", # Downloaded from www.iata.org
  iconWidth = 24,
  iconHeight = 24,
  iconAnchorX = 0,
  iconAnchorY = 0
)

# Create the Leaflet map
leaflet(data = india_airports) %>%
  setView(lat = 18, lng = 77, zoom = 4) %>%
  addProviderTiles(providers$Esri.NatGeoWorldMap) %>%
  addMarkers(
    icon = iata_icon,
    popup = popup
  )

Figure 12: Indian Airports with IATA Logo and Popup

It is possible to create a list of icons, so that different Markers can have different icons. There are some ideas about this at Using Leaflet Markers @JLA-Data.net

Points using `sf` objects

We will use data from an sf data object. This differs from the earlier situation where we had a simple data frame with lon and lat columns. In sf, as we know, the lon and lat info is embedded in the geometry column of the sf data frame.

The tmap package has a data set of all World metro cities, titled metro. We will plot these on the map and also scale the markers in proportion to one of the feature attributes, pop2030. The popup will be the name of the metro city. We will also use the CartoDB.Positron base map.

Note that the metro data set has a POINT geometry, as needed!

Show the Code

data(metro, package = "tmap")
metro

Show the Code

leaflet(data = metro) %>%
  setView(lat = 18, lng = 77, zoom = 4) %>%
  # Add CartoDB.Positron
  addProviderTiles(providers$CartoDB.Positron) %>% # CartoDB Basemap

  # Add Markers for each airport
  addCircleMarkers(
    radius = ~ sqrt(pop2030) / 350,
    color = "red",
    popup = paste(
      "Name: ", metro$name, "<br>",
      "Population 2030: ", metro$pop2030
    )
  )

We can also try downloading an sf data frame with POINT geometry from say OSM data https://www.openstreetmap.org/#map=16/12.9766/77.5888. Let us get hold of restaurants data in Malleswaram, Bangalore from OSM data:

Show the Code

bbox <- osmdata::getbb("Malleswaram, Bengaluru")
bbox %>%
  as_tibble() %>%
  cbind("Coords" = c("Lon", "Lat"))
locations <-
  osmdata::opq(bbox = bbox) %>%
  osmdata::add_osm_feature(key = "amenity", value = "restaurant") %>%
  osmdata_sf() %>%
  purrr::pluck("osm_points") %>%
  dplyr::select(name, cuisine, geometry) %>%
  dplyr::filter(cuisine == "indian")

locations %>% head()

Table 1: Malleswaram Restaurants

Show the Code

leaflet(
  data = locations,
  options = leafletOptions(minZoom = 12)
) %>%
  addProviderTiles(providers$CartoDB.Voyager) %>%
  # Regular `leaflet` code
  addAwesomeMarkers(
    icon = awesomeIcons(
      icon = "fa-coffee",
      library = "fa",
      markerColor = "blue",
      iconColor = "black",
      iconRotate = TRUE
    ),
    popup = paste(
      "Name: ", locations$name, "<br>",
      "Food: ", locations$cuisine
    )
  )

Figure 13: Malleswaram Restaurants

Fontawesome Workaround**

For more later versions of Fontawesome, here below is a workaround from https://github.com/rstudio/leaflet/issues/691. Despite this some fontawesome icons simply do not seem to show up. Aiyooo….;-()

( Update Dec 2023: Seems OK now…)

leaflet detects sf POINT geometry

Note that leaflet automatically detects the lon/lat columns from within the POINT geometry column of the sf data frame.

5.2 LINESTRING, POLYLINESTRING, and POLYGON Data Sources for `leaflet`

We have seen how to get POINT data into leaflet.

LINE and POLYGON data can also come from a variety of sources:

sf package: MULTIPOLYGON, POLYGON, MULTILINESTRING, and LINESTRING objects (from the sf package)
sp package: SpatialPolygons, SpatialPolygonsDataFrame, Polygons, and Polygon objects (from the sp package)
~~**sp package:SpatialLines, SpatialLinesDataFrame, Lines, and Line objects (from the sp package)~~
maps package:map objects (from the maps package’s map() function); use map(fill = TRUE) for polygons, FALSE for polylines
Matrices:Two-column numeric matrix; the first column is longitude and the second is latitude. Polygons are separated by rows of (NA, NA). It is not possible to represent multi-polygons nor polygons with holes using this method; Sounds very clumsy and better not attempt. Use sfheaders instead (see below) to convert to sf format.
Hand-crafted data using sfheaders: We can use the sfheaders package to hand-create LINE/MULTILINE POLYGON/MULTIPOLYGON geometries and pack them into a sf data frame.
Hand-drawn data using the mapedit package:

The mapedit package

https://r-spatial.org//r/2017/01/30/mapedit_intro.html can also be used to interactively add shapes onto a map and save as an geo-spatial object.

We will concentrate on using sf data into leaflet. We may explore maps, and sfheaders objects at a later date.

Polygons/MultiPolygons and LineString/MultiLineString using `sf` data frames

Let us download College buildings, parks, and the cycling lanes in Amsterdam, Netherlands, and plot these in leaflet.

Show the Code

library(osmdata)
# Option 1
# Gives too large a bbox
bbox <- osmdata::getbb("Amsterdam, Netherlands")
# bbox

# Setting bbox manually is better
amsterdam_coords <- matrix(c(4.85, 4.95, 52.325, 52.375),
  byrow = TRUE,
  nrow = 2, ncol = 2,
  dimnames = list(c("x", "y"), c("min", "max"))
)
amsterdam_coords

     min    max
x  4.850  4.950
y 52.325 52.375

Show the Code

colleges <- amsterdam_coords %>%
  osmdata::opq() %>%
  osmdata::add_osm_feature(
    key = "amenity",
    value = "college"
  ) %>%
  osmdata_sf() %>%
  purrr::pluck("osm_polygons")

parks <- amsterdam_coords %>%
  osmdata::opq() %>%
  osmdata::add_osm_feature(key = "landuse", value = "grass") %>%
  osmdata_sf() %>%
  purrr::pluck("osm_polygons")

roads <- amsterdam_coords %>%
  osmdata::opq() %>%
  osmdata::add_osm_feature(
    key = "highway",
    value = "primary"
  ) %>%
  osmdata_sf() %>%
  purrr::pluck("osm_lines")

cyclelanes <- amsterdam_coords %>%
  osmdata::opq() %>%
  osmdata::add_osm_feature(key = "cycleway") %>%
  osmdata_sf() %>%
  purrr::pluck("osm_lines")

We have 11 colleges, 3372 parks, 309 roads, and 280 cycle lanes in our data.

Show the Code

leaflet() %>%
  addTiles() %>%
  addPolygons(
    data = colleges, color = "yellow",
    popup = ~ colleges$name
  ) %>%
  addPolygons(data = parks, color = "seagreen", popup = parks$name) %>%
  addPolylines(data = roads, color = "red") %>%
  addPolylines(data = cyclelanes, color = "purple")

Figure 14: Amsterdam Colleges and Cycling Lanes

6 Using Raster Data in `leaflet`[Work in Progress!]

So far all the geospatial data we have plotted in leaflet has been vector data.

We will now explore how to plot raster data using leaflet. Raster data are used to depict continuous variables across space, such as vegetation, salinity, forest cover etc. Satellite imagery is frequently available as raster data.

6.1 Importing Raster Data [Work in Progress!]

Raster data can be imported into R in many ways:

using the maptiles package
using the terra package
using the OpenStreetMap package

Show the Code

library(terra)
library(maptiles)
# library(OpenStreetMap) # causes RStudio to crash...

7 Bells and Whistles in `leaflet`: layers, groups, legends, and graticules

7.1 Adding Legends

Show the Code

## Generate some random lat lon data around Bangalore
df <- tibble(
  lat = runif(20, min = 11.97, max = 13.07),
  lng = runif(20, min = 77.48, max = 77.68),
  col = sample(c("red", "blue", "green"), 20,
    replace = TRUE
  ),
  stringsAsFactors = FALSE
)

df %>%
  leaflet() %>%
  addTiles() %>%
  addCircleMarkers(color = df$col) %>%
  ### New Code from here
  addLegend(
    values = df$col, labels = LETTERS[1:3],
    colors = c("blue", "red", "green")
  ) %>%
  addGraticule() %>%
  addScaleBar()

7.2 Using Web Map Services (WMS) [Work in Progress!]

To be included.

8 References

The leaflet package: https://rstudio.github.io/leaflet/
Using Leaflet Markers @JLA-Data.net

R Package Citations

Package	Version	Citation
leaflet	2.2.3	Cheng et al. (2025)
osmdata	0.3.0	Mark Padgham et al. (2017)
rnaturalearth	1.1.0	Massicotte and South (2025)
sf	1.0.21	Pebesma (2018); Pebesma and Bivand (2023)
tmap	4.2	Tennekes (2018)

Cheng, Joe, Barret Schloerke, Bhaskar Karambelkar, Yihui Xie, and Garrick Aden-Buie. 2025. leaflet: Create Interactive Web Maps with the JavaScript “Leaflet” Library. https://doi.org/10.32614/CRAN.package.leaflet.

Mark Padgham, Bob Rudis, Robin Lovelace, and Maëlle Salmon. 2017. “Osmdata.” Journal of Open Source Software 2 (14): 305. https://doi.org/10.21105/joss.00305.

Massicotte, Philippe, and Andy South. 2025. rnaturalearth: World Map Data from Natural Earth. https://doi.org/10.32614/CRAN.package.rnaturalearth.

Pebesma, Edzer. 2018. “Simple Features for R: Standardized Support for Spatial Vector Data.” The R Journal 10 (1): 439–46. https://doi.org/10.32614/RJ-2018-009.

Pebesma, Edzer, and Roger Bivand. 2023. Spatial Data Science: With applications in R. Chapman and Hall/CRC. https://doi.org/10.1201/9780429459016.

Tennekes, Martijn. 2018. “tmap: Thematic Maps in R.” Journal of Statistical Software 84 (6): 1–39. https://doi.org/10.18637/jss.v084.i06.

1 Introduction

2 Setting up R Packages

3 Basic Features of a leaflet Map

4 Add Shapes to a Map

4.1 Add Markers with popups

4.2 Adding Popups to a Map

4.3 Adding Labels to a Map

4.4 Adding Circles and CircleMarkers on a Map

4.5 Adding Rectangles to a Map

4.6 Add Polygons to a Map

4.7 Add PolyLines to a Map

5 Using leaflet with External Geospatial Data

5.1 POINT Data Sources for leaflet

Points using Two-Column Matrices

Points using simple Data Frames

Points using sf objects

5.2 LINESTRING, POLYLINESTRING, and POLYGON Data Sources for leaflet

Polygons/MultiPolygons and LineString/MultiLineString using sf data frames

6 Using Raster Data in leaflet[Work in Progress!]

6.1 Importing Raster Data [Work in Progress!]

7 Bells and Whistles in leaflet: layers, groups, legends, and graticules

7.1 Adding Legends

7.2 Using Web Map Services (WMS) [Work in Progress!]

8 References

R Package Citations

5 Using `leaflet` with External Geospatial Data

5.1 POINT Data Sources for `leaflet`

Points using `sf` objects

5.2 LINESTRING, POLYLINESTRING, and POLYGON Data Sources for `leaflet`

Polygons/MultiPolygons and LineString/MultiLineString using `sf` data frames

6 Using Raster Data in `leaflet`[Work in Progress!]

7 Bells and Whistles in `leaflet`: layers, groups, legends, and graticules