Graduated symbol maps

There are many other effective ways to map statistical data besides choropleth maps. One such example is the graduated symbol map, which represents statistical variation by differently-sized symbols. In this exercise, you'll learn how to use the st_centroid() tool in the sf package to create points at the center of each state to be used as inputs to a graduated symbol map in ggplot2.

This exercise is part of the course

Analyzing US Census Data in R

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Exercise instructions

Use the st_centroid() function to generate point centers for each US state.
When plotting the centers, set the size parameter to estimate to scale the point sizes.
Use the scale_size_continuous() function to adjust the range of sizes on the map.

Hands-on interactive exercise

Have a go at this exercise by completing this sample code.

library(sf)

# Generate point centers
centers <- ___(state_value)

# Set size parameter and the size range
___() + 
  ___(data = state_value, fill = "white") + 
  ___(data = centers, aes(___ = estimate), shape = 21, 
          fill = "lightblue", alpha = 0.7, show.legend = "point") + 
  ___(range = c(1, 20))

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