Plotting a chloropleth map of Australian states - r

Question

I plotted a dot density map of the Australian states and am now trying to plot a chloropleth map of the Australian states using the leaflet package and color each state by the count value. I have the following data frame
state count latitude longitude
Australian Capital Territory 125 ... ...
New South Wales 45
Northern Territory 75
Queensland 12
South Australia 245
Tasmania 4895
Victoria 279
The following is the code I used to plot the dot density map
leaflet(aus_state_counts) %>%
addTiles() %>%
addCircleMarkers(
layerId = ~state,
label = ~state,
radius = ~count
) %>%
fitBounds(lng1 = max(aus_state_counts$longitude) ,lat1 = max(aus_state_counts$latitude),
lng2 = min(aus_state_counts$longitude) ,lat2 = min(aus_state_counts$latitude)
)
I am unsure how to plot the states on the map? Do I need additional information for this?

Answer 1

For a choropleth map you will need some spatial polygon data in the form of a shape file (.shp) or GeoJSON (.geojson). Below should work.
library(sf)
library(leaflet)
library(dplyr)
# GeoJSON Data
states <- read_sf("https://raw.githubusercontent.com/rowanhogan/australian-states/master/states.geojson")
counts <- data.frame(state=c("Australian Capital Territory", "New South Wales", "Northern Territory", "Queensland",
"South Australia", "Tasmania", "Victoria"), count=c(125,45,75,12,245,4895,279))
# Join to count data
data <- states %>%
dplyr::left_join(counts, by=c("STATE_NAME" = "state"))
# Specify choropleth colors
pal <- colorQuantile("Blues", domain = data$count)
# Plot Map
leaflet(data) %>%
addTiles() %>%
addPolygons(fillColor=~pal(count), fillOpacity=0.8, color="white", weight=1)