In Topic 4 of Lesson 1 we will consider the first of two criteria we can use to evaluate an encoding: expressiveness. Expressiveness means that the chosen encoding expresses all of, and only, what’s in the data. To better understand the concept of expressiveness, we’ll consider at examples in which an encoding can fail the expressiveness criteria, such as: 1) by showing ordered data in a way that doesn’t express any order at all, 2) by showing ordered data in a way that expresses the wrong order and 3) by showing unordered data in a way that expresses some order. Expressiveness relates to more than just order, and we’ll consider more scenarios as we go along.
Only ordinal, interval and ratio scales are ordered
Comparing an encoding type that expresses the inherent order of an ordinal variable with two that don’t
Exercise 1.4. In the Lesson 1 Exercise Worksheet or on a sheet of blank paper, sketch marks that express the three (unordered) levels of the nominal variable on the left. Then sketch different marks that express the three (ordered) levels of the ordinal variable on the right:
Eye color (blue, brown, green):
Temp level (cold, moderate, hot):
“Graphic design issues are codified with expressiveness and effectiveness criteria. Expressiveness criteria identify graphical languages that express the desired information. Effectiveness criteria identify which of these graphical languages, in a given situation, is the most effective at exploiting the capabilities of the output medium and the human visual system.”