Chapter 3 Variables

In statistical learning, the most typical data format involves a set of individuals or objects described by several characteristics commonly known as variables. Likewise, the most common format in which data is organized is in a table with columns representing variables, and rows representing individuals, like in the following figure.

Figure 3.1: Conceptual table of individuals and variables

Before moving onto more matrix algebra concepts, we need to discuss a couple of things about variables in terms of how they can be classified, and also how users tend to encode values in them.