Maps with {shiny} Pt 2


Steven P. Sanderson II, MPH


May 5, 2023


The code provided at the end of this post is an example of how to create a simple Shiny app in R that utilizes the OpenStreetMap (OSM) API to create a map of amenities in a specific location.

The app has two main parts: the user interface (UI) and the server.

The UI section is defined using the fluidPage function from the Shiny library, which creates a responsive, fluid layout for the app. It includes a title panel, a sidebar panel with text input fields for the city, state, country, and amenity type, and a submit button. The main panel of the UI includes a leafletOutput object, which will display the map of amenities.

The server section is defined using the server function from the Shiny library. This function is responsible for processing the inputs from the UI, performing any necessary calculations, and rendering the output.

The observeEvent function is used to capture the click event of the submit button. When the button is clicked, the function getbb from the osmdata library is used to retrieve the bounding box (bbox) for the specified location.

Next, the opq function from the osmdata library is used to create a query object that searches for amenities of the specified type (input$amenity) within the retrieved bbox.

The assign function is used to set a variable has_internet_via_proxy to TRUE in the curl environment. This is necessary to ensure that the osmdata_sf function, which downloads the OSM data, works properly.

The osmdata_sf function is then called with the created query object as its argument. This function downloads the OSM data and converts it to an sf object. The resulting sf object contains a data frame with information about the amenities found in the specified location.

A mapview object is then created using the osm_points part of the sf object. This object is assigned to the variable m.

Finally, the renderLeaflet function is used to display the resulting map. The mapview object m is accessed and its @map attribute is used as the input to the renderLeaflet function. This displays the map of amenities in the specified location.

There is also some commented out code in the server section that provides an alternative way to display the map using the leaflet library instead of the mapview library. This code creates a leaflet object, adds tiles to the map, and then adds circle markers to represent the amenities found in the specified location. The popup argument specifies what information is displayed in the popups that appear when the user clicks on a marker.

Overall, this code demonstrates how to use the Shiny library to create an interactive web application that utilizes the OSM API to display maps of amenities in specific locations.

Full Application

As usual, here is the full code. Please take it and see what you can do with it.


ui <- fluidPage(
  titlePanel("Mapping with Shiny"),
      textInput("city", "City", placeholder = "e.g. Queens"),
      textInput("state", "State", placeholder = "e.g. New York"),
      textInput("country", "Country", placeholder = "e.g. USA"),
      textInput("amenity", "Amenity Type", placeholder = "e.g. pharmacy"),
      actionButton("submit", "Submit")

server <- function(input, output, session) {
  observeEvent(input$submit, {
    # Concatenate city, state, and country inputs into a single string
    address <- paste(input$city, input$state, input$country, sep = ", ")
    bbox <- getbb(address)
    query <- opq(bbox = bbox) |>
      add_osm_feature(key = "amenity", value = input$amenity)
    assign("has_internet_via_proxy", TRUE, environment(curl::has_internet))
    sf_obj <- osmdata_sf(query)
    m <- mapview(sf_obj$osm_points)
    output$map <- renderLeaflet({
    # output$map <- renderLeaflet({
    #   leaflet(sf_obj$osm_points) |>
    #     addTiles() |>
    #     addCircleMarkers(
    #       radius = 3, 
    #       popup = ~as.character(
    #         paste(
    #           "Name: ", name, "<br/>",
    #           "OSM ID: ", osm_id, "<br/>"
    #         )
    #       ),
    #       opacity = 0.3
    #     )
    # })

shinyApp(ui, server)