R Shiny: Make a reactive map of state by county

[Nia711]

I would like to use leaflet to make a map of Virginia with county boundaries. Can I use the upmaps package in anyway? Or do I have to use a shapefile. Does anyone have any ideas. I just started learning R, and am not sure how to do this.

[Nia711]

I am also wondering if there is a way to layer the usmaps package on leaflet

[jlacko]

I suggest you base your map on county boundaries from the {tigris} package. It is easy to use and rather popular.

Your app with a reactive map might look kind of like this:

library(shiny)
library(leaflet)
library(sf)

# VA counties - downloaded via the awesome tigris package
shape <- tigris::counties(state = "VA", class = "sf")


# Define UI 
ui <- fluidPage(

    # Application title
    titlePanel("The Old Dominion"),

    # Top panel with county name
    verticalLayout(
        
        wellPanel(textOutput("cnty")),

        # the map itself
        mainPanel(
           leafletOutput("map")
        )
    )
)

# Define server logic       
server <- function(input, output) {
    
    output$map <- renderLeaflet({
        leaflet() %>% 
            addProviderTiles("Stamen.Toner") %>% 
            addPolygons(data = shape, 
                        fillColor = "aliceblue", 
                        color = "grey",
                        layerId = ~COUNTYNS)
    })
    
    # this is the fun part!
    observe({ 
        event <- input$map_shape_click
        output$cnty <- renderText(shape$NAMELSAD[shape$COUNTYNS == event$id])

    })
}

# Run the application 
shinyApp(ui = ui, server = server)

I am using reactivity to display the county name on top (by reading the id of clicked polygon - it has to be assigned to layerId argument of the leaflet call; once a polygon is clicked it is in input$map_shape_click$id field).

[Nia711]

Thank you so much, I will try that