Lab 2 Tutorial | PAF 516

What You Will Build

In this lab you will take the Economic Hardship Index from Lab 1 and apply advanced cartographic techniques: comparing classification methods, building bivariate choropleths, creating interactive GPU-rendered maps, and producing publication-quality figures with scale bars and north arrows.

The tutorial walks through every step with fully working code. Knit it first to see the finished product, then go back and run chunk by chunk to understand how it works.

Learning Objectives

Apply and compare four classification methods (quantile, Jenks, equal interval, standard deviation)
Explain how classification method choice affects map interpretation and policy conclusions
Create a bivariate choropleth map using the biscale package
Build an interactive mapgl map with tooltips, hover effects, and GPU-rendered tiles
Apply cartographic design principles: scale bars, north arrows, and professional annotation
Understand the Modifiable Areal Unit Problem (MAUP) and its implications for policy

Before You Begin

1 — File and Folder Setup

Create this folder structure before downloading anything. Move the downloaded .qmd into PAF516/Lab2/ before opening it in RStudio.

PAF516/
  Lab1/  ...
  Lab2/
    Lab2_Tutorial.qmd            ← downloaded tutorial (do not edit)
    Lab2_Tutorial.html           ← auto-generated when you knit
    Lab2_Assignment_Howell.qmd   ← your renamed assignment copy
    Lab2_Assignment_Howell.html  ← submit this to Canvas
  Lab3/  Lab4/  ...

2 — Install Packages (Run Once)

Do this before knitting

Open Lab2_Tutorial.qmd in RStudio
Click inside the packages chunk (labeled #| label: packages)
Press Cmd+Return (Mac) or Ctrl+Enter (PC) to run just that chunk
Wait — first run downloads and installs packages and may take 5–10 minutes
After it finishes, future knits will be fast — the renv block only runs once automatically

What is renv?

renv records the exact version of every package used so that code that works today still works next semester.

3 — Census API Key

The lab pulls live data from the Census Bureau. If you don't have a key yet:

Register free at api.census.gov/data/key_signup.html
Check email for your key (arrives within a few minutes)
In the RStudio console run: census_api_key("YOUR_KEY_HERE", install = TRUE)
Restart R: Session → Restart R

Running the Tutorial

Option A — Knit First (Recommended)

Click the Render button (blue arrow, top of editor) or press Cmd+Shift+K / Ctrl+Shift+K. This produces Lab2_Tutorial.html with all results — classification comparison maps, bivariate choropleths, and the interactive mapgl map. Review the output to see what the completed analysis looks like.

Option B — Run Chunk by Chunk (Best for Learning)

Place your cursor inside any code chunk and press the run shortcut. Output appears inline. Fix any errors before moving on. This is how you understand what each step does.

Action	Mac	PC
Run current chunk	`Cmd+Return`	`Ctrl+Enter`
Run all chunks above	`Cmd+Option+P`	`Ctrl+Alt+P`
Knit / Render	`Cmd+Shift+K`	`Ctrl+Shift+K`

What's Inside

Step	What It Does
Step 1	Pull Census data and build the hardship index at the block group level (Maricopa County)
Step 2	Compare four classification methods (quantile, Jenks, equal interval, standard deviation) as a 2×2 small-multiple grid
Step 3	Create a bivariate choropleth mapping hardship × percent minority using `biscale`
Step 4	Build an interactive `mapgl` map of Maricopa County block groups with tooltips and hover effects
Step 5	Create a publication-quality map with scale bar and north arrow using `ggspatial`
Step 6	Explore the Modifiable Areal Unit Problem (MAUP) with an interactive US county hardship map

Download

Lab 2 Tutorial File

Download Lab2_Tutorial.qmd

Right-click → Save Link As. Save directly to your PAF516/Lab2/ folder. Do not open in the browser.