Exercise

# Useful double axes

Double x and y-axes are a contentious topic in data visualization. We'll revisit that discussion at the end of chapter 4. Here, I want to review a great use case where double axes actually do add value to a plot.

Our goal plot is displayed in the viewer. The two axes are the raw temperature values on a Fahrenheit scale and the transformed values on a Celsius scale.

You can imagine a similar scenario for Log-transformed and original values, miles and kilometers, or pounds and kilograms. A scale that is unintuitive for many people can be made easier by adding a transformation as a double axis.

Instructions 1/3

**undefined XP**

Begin with a standard line plot, of `Temp`

described by `Date`

in the `airquality`

dataset.