How do I present quantitative data with position?

Perception
#1

Hello,

in a book about data visualization I came across the Bertin’s visual variables. There is size, shape, value, hue, texture, orientation and position. The book states, that we can present quantitative data with size, value and position. I agree with size and value, but I do not understand how I can present quantitative data with position. For a larger integer, I can for example increase the size of the point and make it darker (value). If someone could provide me an example for position, I would be very thankful.

Looking forward to your answers. Greetings ProblemStudent.

#2

In CLEVELAND and McGILL, Graphical Perception: Theory Experimentation, and Application to the Development of Graphical Methods, position (as a visual variable) is defined with a common base-axis (e.g., a common zero line). In an experiment, they compare bars in a bar chart that start from the same base axis, and bars that do not share any base axis. They use the former for position perception, and latter for size perception.

Of course, the shape of bars may appear to be a size variable. However, in the former case, the bars can be replaced by a dot or line marker at the top of the bar (without showing bars explicitly) assuming the base axis is at the bottom. A box plot has both position and size variables.