Chart Rules, As Simple as Possible, But Not Any Simpler!

In chart design it’s good to make things simple, but you certainly should avoid oversimplification. As Einstein said:

"Things should be made as simple as possible, but not any simpler"

Seth Godin presented in his blog The three laws of great graphs:

1. One Story
2. No Bar Charts
3. Motion

Effective chart design rules are simple, but reducing it to this set of 3 rules certainly is an over-oversimplification.

Particularly rule 2 is flawed. Seth details rule 2:

"NO BAR CHARTS
Bar charts are dramatically overrated, primarily because they’re the first choice in many graphing programs.

The problem with bar charts is that they should either be line/area charts (when graphing a change over time, like unemployment rates) or they should be a simple pie chart (when comparing two or three items at the same scale).

Jorge, Kaiser and Jon already wrote some critical posts about this rule, where Jon suggested to replace rule 2 with

Choose Chart Types Intelligently

We are working tightly together with Stephen Few on a new product that helps business users creating effective charts with Excel and are therefore we are quite familiar with Stephen’s design principles.

Its an easy to learn set of rules

1. Determine the relationship you want to display

Relationship	Sample
Value Comparison	Sales in different regions
Ranking	Best selling products
Time-Series	Sales in the last 12 months
Part-to-Whole	Market shares
Deviation	Revenue Actual vs Budget in the last 12 months
Distribution	Support response times
Correlation	Relationship between employee’s heights in inches and their salary

2. Determine if you want to emphasize individual values or the overall pattern
3. Determine the chart type

Relationship	Encoding Method
Value Comparison	Bars and Columns
Ranking	Bars and Columns
Time-Series	Lines to emphasize the overall trends or pattern
	Points connected by lines to slightly emphasize individual values
	Columns to emphasize and support comparisons between individual values
Part-to-Whole	Bars and Columns
Deviation	Lines to emphasize the overall shape of the data
	Points connected by lines to slightly emphasize individual data points
	Bars and Columns to emphasize individual values
Distribution	Columns to emphasize individual values
	Lines to emphasize the overall shape of he data
Correlation	Points and a trend line in the form of a scatter plot