Mapping Polygons

Interactive Maps with leaflet in R

Rich Majerus

Vice President of Strategy & Planning, Queens University of Charlotte

Plotting Polygons

shp %>% 
  leaflet() %>% 
  addTiles() %>% 
  addPolygons()

All NC zips 1

addPolygons()

weight - the thickness of the boundary lines in pixels
color - the color of the polygons
label - the information to appear on hover
highlight - options to highlight a polygon on hover

shp %>% 
leaflet() %>% 
addTiles() %>% 
addPolygons(weight = 1,
            color = "grey",
            label = ~paste0("Total Income: " dollar(income)),
            highlight = highlightOptions(weight = 3, color = "red",
                                         bringToFront = TRUE))

addPolygons()

All NC zips 2

Coloring Numeric Data

colorNumeric

nc_pal <- colorNumeric(palette = "Blues", 
                       domain = high_inc@data$mean_income)

colorBin

nc_pal <- colorBin(palette = "YlGn", bins = 5,
                   domain = high_inc@data$mean_income)

colorQuantile

nc_pal <- colorQuantile(palette = "YlGn", n = 4, 
                        domain = high_inc@data$mean_income)

colorNumeric()

nc_pal <- colorNumeric("Blues", domain = high_inc@data$mean_income)

previewColors(pal = nc_pal, 
              values = c(seq(100000, 600000, by = 100000)))

previewColors()

Choropleth Map

nc_pal <- colorNumeric(palette = "Blues", 
                       domain = shp@data$mean_income)

shp %>% 
  leaflet() %>% 
  addTiles()  %>% 
  addPolygons(weight = 1, fillOpacity = 1,
              color =  ~nc_pal(mean_income),
              label = ~paste0("Mean Income: ", 
                              dollar(mean_income)),
              highlight = highlightOptions(weight = 3,
                                           color = "red",
                                           bringToFront = TRUE))

Choropleth Map

NC income choropleth

Choropleth Example

ggplot(shp@data,
       aes(mean_income)) +
  geom_histogram()

Income histogram

ggplot(shp@data, 
        aes(log(mean_income))) +
  geom_histogram()

Logged income histogram

Logging

NC logged income choropleth 1

Let's practice!

Interactive Maps with leaflet in R