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.

2D

2 axes (horizontal, x; vertical, y)

Points

Lines

Bars

Boxes

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,
- length/height

Easy to compare lengths to determine relative magnitude.

Discrete values, not connected.

Bars

*can*be used for connected values (e.g., time series) when:- you want to compare individual values at specific times, or
- histogram

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)