Jun 24 2015
5 min

Leaflet: Interactive web maps with R

We are excited to announce that a new package leaflet has been released on CRAN. The R package leaflet is an interface to the JavaScript library Leaflet to create interactive web maps. It was developed on top of the htmlwidgets framework, which means the maps can be rendered in R Markdown (v2) documents, Shiny apps, and RStudio IDE / the R console. Please see http://rstudio.github.io/leaflet for the full documentation. To install the package, run


We quietly introduced this package in December when we announced htmlwidgets, but in the months since then we’ve added a lot of new features and launched a new set of documentation. If you haven’t looked at leaflet lately, now is a great time to get reacquainted!

The Map Widget

The basic usage of this package is that you create a map widget using the leaflet() function, and add layers to the map using the layer functions such as addTiles(), addMarkers(), and so on. Adding layers can be done through the pipe operator %>% from magrittr (you are not required to use %>%, though):


m <- leaflet() %>%
  addTiles() %>%  # Add default OpenStreetMap map tiles
  addMarkers(lng=174.768, lat=-36.852,
    popup="The birthplace of R")
m  # Print the map


There are a variety of layers that you can add to a map widget, including:

  • Map tiles

  • Markers / Circle Markers

  • Polygons / Rectangles

  • Lines

  • Popups

  • GeoJSON / TopoJSON

  • Raster Images

  • Color Legends

  • Layer Groups and Layer Control

There are a sets of methods to manipulate the attributes of a map, such as setView() and fitBounds(), etc. You can find the details from the help page ?setView.

The leaflet() function and all layer functions have a data argument that can take several types of spatial data objects, including matrices and data frames with latitude and longitude columns, spatial objects from the sp package (e.g. SpatialPoints and SpatialPointsDataFrame, etc), and the data frame returned from maps::map(). When you have got a data object in leaflet() or layer functions, you may use the formula interface to pass values of variables to function arguments.

m <- leaflet(df) %>% addTiles()
m %>% addCircleMarkers(radius = ~size, color = ~color)
# this is more compact than radius = df$size, color = df$color


You can add basemaps to a map widget using map tiles. The default tiles provided by addTiles() are OpenStreetMap tiles, and you can easily add third-party tiles via addProviderTiles(). WMS (Web Map Service) tiles can be added via addWMSTiles(). You may use more than one tile layer on a map, too.

Markers and Popups

Icon markers and circle markers can be placed at the locations specified by latitudes/longitudes on a map via addMarkers() and addCircleMarkers(), respectively. You can change the default appearance of icon markers (dropped pins) and use custom icon images, and you can also customize the appearance of circle markers (radius, color, and so on). When there are a large number of markers on a map, you may cluster them into groups (each group containing multiple markers close to each other), and see individual markers as you zoom into the map. When you add a marker to a map, you can also bind a popup to it through the popup argument, so users can see more information after they click on the marker. It is possible to add popups separately without markers as well via addPopups().

Lines and Shapes

Polygons, polylines, circles, and rectangles can be added to the map through addPolygons(), addPolylines(), addCircles(), and addRectangles(). For example, you can create a choropleth map by adding polygons with different colors.


When your data is in the GeoJSON or TopoJSON format, you can add it to the map using addGeoJSON() and addTopoJSON(), respectively. The features in the JSON data can be styled via either the styles specified inside the data, or the arguments of the functions addGeoJSON()/addTopoJSON().

Raster Images

Two-dimensional RasterLayer objects (from the raster package) can be turned into images and added to Leaflet maps using the addRasterImage() function. You can color the image through the colors argument that accepts a variety of color specifications.

Shiny Integration

Like most Shiny output widgets, you just create a leaflet output element in the UI using leafletOutput(), and render the widget on the server side using renderLeaflet(), with a leaflet widget object passed to renderLeaflet().

After a widget is rendered in Shiny, you may modify it using the leafletProxy() object. All you need to do is replace leaflet() with leafletProxy(). For example, suppose the output ID of the map is mymap, and you have two numeric inputs x and y (specifying lng and lat) in the app, then you can add new markers to the map via:

  leafletProxy("mymap") %>% addMarkers(input$x, input$y)

If you added layers with layer ID’s to a map, you will be able to remove certain layers according to the layer ID’s (e.g. removeMarker()). You can also clear entire layers (e.g. clearMarkers()).

When interacting with a map or its layers, you can obtain some information about the interaction from the Shiny input object. For example, input$mymap_shape_click will be a list of the form list(lat = lat, lng = lng, id = layerId) after you click on a shape object (e.g. a marker or a circle) on the map.

Color Palettes and Legends

We have provided four types of color palettes in this package: colorNumeric(), colorBin(), colorQuantile(), and colorFactor(). These palette functions return functions that can be applied to numeric or factor values to generate colors. If you have used one of these color palettes, you may also use addLegend() to add a color legend to the map.

Layer Groups and Layer Control

Normally a layer function has an argument called group, which can be used to assign multiple layer elements into a group. Later you may use addLayersControl() to add a layer control to the map to show/hide groups.

We hope you will enjoy using this package. Please let us know if you have any comments or questions when the R package documentation or the website http://rstudio.github.io/leaflet is not clear enough. You are welcome to file bug reports / feature requests to the Github repository or ask questions in the shiny-discuss mailing list.

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