How do I integrate multiple choropleth maps made with Leaflet in Shiny?

Question

I have created three separate choropleth maps in Leaflet, all are across Europe with the same countries being used. Each choropleth map shows a different type of ratio and has two layers for 1999 and 2009.

Whilst I have successfully integrated the choropleth maps individually to Shiny with the year layers, I want to be able to just have one Shiny map with a drop down bar to click between the three different choropleth maps, whilst still keeping my layers for each map.

Can anyone suggest how to do this?

Answer 1

You can use a leafletProxy for that. I slightly modified the example from here to better suit what you are asking for. Hope this helps!

library(shiny)
library(leaflet)

ui <- bootstrapPage(
  tags$style(type = "text/css", "html, body {width:100%;height:100%}"),
  leafletOutput("map", width = "100%", height = "100%"),
  absolutePanel(top = 10, right = 10,
                selectInput("maptype", "Map type: ",
                            choices = c("map 1", "map 2", "map 3")
                )
  )
)

server <- function(input, output, session) {

  # Reactive expression for the data subsetted to what the user selected
  filteredData <- reactive({
    if(input$maptype=="map 1") return(quakes[sample(1:nrow(quakes),50,replace=TRUE),])
    if(input$maptype=="map 2") return(head(quakes,50))
    if(input$maptype=="map 3") return(tail(quakes,50))

  })


  output$map <- renderLeaflet({
    leaflet(quakes) %>% addTiles() %>%
      fitBounds(~min(long), ~min(lat), ~max(long), ~max(lat))
  })

  observe({
    leafletProxy("map", data = filteredData()) %>%
      clearShapes() %>%
      addCircles(radius = ~10^mag/10, weight = 1, color = "#777777", fillOpacity = 0.7, popup = ~paste(mag)
      )
  })


}

shinyApp(ui, server)