There's a few arbitrary codes/conventions to learn at the start. My take is not to look too deeply into them - every DSL/framework has them and in ggplot2's cas

There's a few arbitrary codes/conventions to learn at the start. My take is not to look too deeply into them - every DSL/framework has them and in ggplot2's case they only take a very short time to get used to before you have the flexibility and incredible power/productivity of ggplot2 at your fingertips!