Evaluating the Quality of a Visual Encoding

There are 2 principles when it comes to evaluating the quality of a visual encoding:

• expressiveness

• effectiveness

Expressiveness: The visual representation should represent all and only the relationships that exist in the data. For example, ordered data must not appear as unordered and vice versa. This principle, if followed, makes sure that all the necessary information is communicated and no misinformation is conveyed i.e. we do not convey any information that isn't present in our data.

Effectiveness: The relevance of the information should match the effectiveness of the channel. The image below shows the effectiveness of different channels to represent ordered (and quantitative) and categorical attributes.

It can be concluded that position (and spatial regions) are the most effective channels. Therefore, we must pay special attention while determining the position of objects in a graph.