One of the best ways to get a handle on how the grammar works is to apply it to the analysis of existing graphics. For each of the graphics listed below, write down the components of the graphic. Don’t worry if you don’t know what the corresponding functions in ggplot2 are called (or if they even exist!), instead focussing on recording the key elements of a plot so you could communicate it to someone else.
“Napoleon’s march” by Charles John Minard: http://www.datavis.ca/gallery/re-minard.php
“Where the Heat and the Thunder Hit Their Shots”, by Jeremy White, Joe Ward, and Matthew Ericson at The New York Times. http://nyti.ms/1duzTvY
“London Cycle Hire Journeys”, by James Cheshire. http://bit.ly/1S2cyRy
The Pew Research Center’s favorite data visualizations of 2014: http://pewrsr.ch/1KZSSN6
“The Tony’s Have Never Been so Dominated by Women”, by Joanna Kao at FiveThirtyEight: http://53eig.ht/1cJRCyG.
“In Climbing Income Ladder, Location Matters” by the Mike Bostock, Shan Carter, Amanda Cox, Matthew Ericson, Josh Keller, Alicia Parlapiano, Kevin Quealy and Josh Williams at the New York Times: http://nyti.ms/1S2dJQT
“Dissecting a Trailer: The Parts of the Film That Make the Cut”, by Shan Carter, Amanda Cox, and Mike Bostock at the New York Times: http://nyti.ms/1KTJQOE