CHART DESIGN PRINCIPLES

ADAPTED FROM MIKE ALEXANDER’S PELTIER TECH BLOG*

*http://peltiertech.com/WordPress/ten-chart-design-principles-guest-post/

Avoid fancy formatting

Avoid flamboyant color

Primary colors usually preferable

Focus on the data, not the graphics

Fancy Plain

Avoid unnecessary clutter

Less clutter

Simplify large numbers

Sort data

Unsorted Sorted

Limit pie chart use

" The Trailer Trash of Charting"

Why limit pie charts?

Because they

take more space than line and bar charts

don’t clearly represent more than two or three data categories

don’t show negative values well It’s easier to compare size when length,

ratherm than area is used

The graphic was created by User:Schutz for Wikipedia on 28 August 2007)

Three sets of data plotted using pie charts & bar charts.

Identifiers too far from the data

If moved nearer, data overlaps

Bar charts solve these problems

When and how to use a pie chart

Can you define the entire set in a way that makes sense to the viewer?

Is the goal to compare a part to the whole, one slice to the pie?

Are there five parts or less? Is size differences obvious? Less than 7 degrees of arc will

not be noticed.

If yes to the above - Use distinct colors and clear labels

From Using Graphics & Understanding Pie Charts

In line charts, maintain appropriate aspect ratios

A skewed aspect ratio* distorts Too tall exaggerates

the trend

* Aspect ratio = ratio of the width of the image to its height

Too wide flattens the

trend.

Find the appropriate (& ethical) aspect ratio

Width about twice as long as the height is tall.

Is a chart the most effective choice?

Use a chart when you want your readers to see

TrendsRelationshipsComparisons

Excel’s 12 Standard Charts

Column charts Bar charts Line charts Pie charts XY (Scatter) charts Area charts Doughnut charts Radar charts Surface charts Bubble charts Stock charts Cylinder, Cone, or Pyramid charts

A simple table may better

Or even a “single-number semi table”*

*A term of interface designer Edward Tufte

New York Times, March 20, 2003, p. D1

Write effective captions

In captions and the text, verbs show movement upward or downward

Declined Dropped Sank Rose Increased Grew

And highlight sudden movement Fell Shot up Rocketed Surged Plummeted Plunged Reached a peak Sank to a trough

or no movement

Remained steady Were unchanged Did not change Remained constant Remained stable Stabilized Stagnated

Further study

Some Graphic and Semi-graphic Displays, John W. Turkey (advanced)

Using Graphics (basic) Understanding Pie Charts, Eagereyes,

Robert Kosara MS Office Chart Types