Best medium (table/graph type).
Designing graph to convey message.
Data graphics ~ verbal language
The rules of graphical communication are rarely arbitrary
Usually based on an understanding of visual perception:
How we see,
Visually encode information for easy and accurate decoding by audience.
2 axes (horizontal, x; vertical, y)
Pinpoint specific location on graph,
Encode values associated with scale on each axis.
Shapes (dots, squares), filled/open.
YES: dot plot, strip plot, scatter plot.
NO: time series.
Lines connect points.
Encode values by location.
Ends of line segments mark values.
Overall shape of data values.
Slope is meaningful.
YES: time series.
Overall shape & individual values.
Multiple time series.
Lines should only connect points that are related/connected.
Encode values 2 ways:
location of end point,
Easy to compare lengths to determine relative magnitude.
Discrete values, not connected.
Bars can be used for connected values (e.g., time series) when:
Values change through time (e.g., $ per mo.)
Values ordered by size (e.g., sales, population)
Values represent parts/proportions of a whole (e.g., relative cover, regional sales)
Values represent the difference between two sets of values (e.g., income vs outgoing)
Counts of values per interval/bin (e.g., number of trees per size class)
Comparison of two paired sets of values (e.g., height vs weight)
Values displayed on a map (e.g., population per city, species richness per site)
Values are compared for unordered categories (e.g., regions, fruit type)