An ordinal scale maps a discrete value to some other value. A discrete value is something that can't be divided. Previously, we've used values such as numbers that can be divided up and interpolated. Interpolated just means that for any two numbers, we can find other numbers in between them. For instance, given 10 and 5, we can find values between them (6, 8.2, 7, 9.9, and so on). Now, we want to map values that can't be interpolated—the label properties in our dataset (Bob, Sally, Matt, and Jane). What values lie between Bob and Sally? What about between Bob and Matt? There are none. These are just strings, not numerical values that can be divided up and interpolated.
What we want to do is map these discrete values ...
