CODEWITHSUNDEEP
rleafletgischoropleth
firmo23
firmo23

Reputation: 8404

How to create a leaflet choropleth map of US counties

With the code below I get my dataframe with US county data

library(raster)
library(leaflet)
library(tidyverse)

# Get USA polygon data
USA <- getData("GADM", country = "usa", level = 2)

### Get data
mydata <- read.csv("https://www.betydb.org/miscanthus_county_avg_yield.csv",
                   stringsAsFactors = FALSE)

My object is to crate an interactive leaflet choropleth map of Avg_yield so first I fortify my USA polygon data

library(rgeos)
library(maptools)
library(ggplot2)
states.shp.f <- fortify(USA, region = "NAME_2")

Then I subset my dataset and merge it with the fortified:

mydata2<-mydata[,c("COUNTY_NAME","Avg_yield")]
colnames(mydata2)[1]<-"id"

## merge shape file with data
merge.shp.coef <- merge(states.shp.f, mydata2, by = "id")

but now I have a dataset with every county name many times and also some counties have different values of Avg_yield. Whats the proper way to process those data in order to use the leaflet code like:

leaflet() %>% 
  addProviderTiles("OpenStreetMap.Mapnik") %>%
  setView(lat = 39.8283, lng = -98.5795, zoom = 4) %>%
  addPolygons(data = USA, stroke = FALSE, smoothFactor = 0.2, fillOpacity = 0.3,
              fillColor = ~mypal(mydata$Avg_yield),
              popup = paste("Region: ", USA$NAME_2, "<br>",
                            "Avg_yield: ", mydata$Avg_yield, "<br>")) %>%
  addLegend(position = "bottomleft", pal = mypal, values = mydata$Avg_yield,
            title = "Avg_yield",
            opacity = 1)

Upvotes: 2

Views: 2226

Answers (1)

Oscar Jnn
Oscar Jnn

Reputation: 154

The propoer way to do this is to transform your polygon object into a sf object with st_as_sf()

Here you have a working example : (I did used some other data for the polygon, I thought yours too precise and require a lot of resources, plus I made it work with shiny)

library(leaflet)
library(tidyverse)
library(ggplot2)
library(sf)
library(shiny)

USA <- st_read(dsn = '[your path]/cb_2018_us_county_500k.shp')

### Get data
mydata <- read.csv("https://www.betydb.org/miscanthus_county_avg_yield.csv",
                   stringsAsFactors = FALSE)

states_sf <- st_as_sf(USA)

mydata2<-mydata[,c("COUNTY_NAME","Avg_yield")]
colnames(mydata2)[1]<-"NAME"

## merge shape file with data
states_sf_coef <- left_join(states_sf, mydata2, by = "NAME")


ui <- fluidPage(

  leafletOutput("map", height = "100vh")
)

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

  bins <- c(0, 5, 10, 15, 20, 25, 30, 35, 40)
  mypal <- colorBin("YlOrRd", domain = states_sf_coef$Avg_yield, bins = bins)

  #Sortie map
  output$map <- renderLeaflet({
    leaflet()%>%
      addProviderTiles("OpenStreetMap.Mapnik")%>%
      setView(lat = 39.8283, lng = -98.5795, zoom = 4) %>%
      addPolygons(
        data = states_sf_coef,
        fillColor = ~mypal(states_sf_coef$Avg_yield),
        stroke = FALSE,
        smoothFactor = 0.2,
        fillOpacity = 0.3,
        popup = paste("Region: ", states_sf_coef$NAME_2, "<br>",
                      "Avg_yield: ", states_sf_coef$Avg_yield, "<br>"))%>%
      addLegend(position = "bottomleft",
                pal = mypal,
                values = states_sf_coef$Avg_yield,
                title = "Avg_yield",
                opacity = 1)
  })

}

# Create Shiny app ----
shinyApp(ui = ui, server = server)

Upvotes: 4

Related Questions