The R Book, 3rd Edition

6Graphics in More Detail

We looked at the basics of plotting in in Chapter . Here, we delve into more detail, under the following broad topics:

• Colour in plots;
• Changing the look of graphics;
• Adding items to plots;
• An introduction to an alternative plotting system using ggplot2.

We end the chapter with the ultimate graphics cheat‐sheet, which goes through a large number of plotting options alphabetically.

6.1 More on colour

Colour can make or break a plot, and it's often tricky to find a set of colours that is easy on the eye and also provides good contrast. In this section, we'll start with colour choice, before looking at how to change the colour of various elements of a plot.

6.1.1 Colour palettes with categorical data

Rather than choose a set of colours explicitly, it's possible to use a colour palette. It is easy to create a vector of colours from a palette, then refer to the colours by their subscripts within the palette. The key is to create the right number of colours for our needs.

Here's a simple example where we use the built‐in heat.colors () to shade the temperature bars in our Silwood Weather dataset. We want the colours to grade from cold to hot, then back to cold again from January to December as in Figure 6.1:

Figure 6.1 Shaded boxplots of temperature ...