Models with a single variable can be useful (if you want to remove a single strong trend), but almost every real model contains multiple variables. In this unit, you’ll learn how to visualise these more complicated models, including models for categorical data (i.e. factors).
You already read the following chapter as part of the Fitting and visualizing models unit, but it’s relevant for this unit as well. Review the chapter, paying attention to the parts that discuss building and interpreting models with multiple variables.