How Many Words
is a Picture Worth?
Introducing Effective Data Visualization:
Statistical Figures and Visual Maps
Dr. Jim Lee, Associate Director of the
Center for Teaching, Research and Learning
and
Adjunct Professorial Lecturer in the
School of International Service
March 19, 2012
Statistical Figures
1.
2.
3.
4.
5.
Scatter plots
Trend Lines
Pie Charts
Bar Charts
Area Charts
1.
Scatter Plots
Be Aware of Scales, Avoid White Space
[Note: Redefine X axis]
Development and Population Concentration in Largest City in Latin America & the Caribbean, 2005
Population in the largest city (% of urban population)
200.0
180.0
160.0
140.0
Grenada
120.0
Barbados
100.0
Antigua & Barbuda
St. Kitts & Nevis
80.0
Suriname
Guyana
60.0
Uruguay
Panama
Chile
Paraguay
40.0
The Bahamas
Trinidad & Tobago
23.8
20.0
Colombia
Venezuela
Guatemala Brazil
0
5000
10000
15000
20000
25000
GDP per capita in Constant $
30000
35000
40000
Use Proper Scaling to Show Data Differentiation
A third dimension could use single color intensities
Development and Population Concentration in Largest City in Latin America & the Caribbean, 2005
Population in the largest city (% of urban population)
140.0
Grenada
120.0
Barbados
100.0
Antigua & Barbuda
The Bahamas
St. Kitts & Nevis
80.0
Guyana
60.0
Suriname
Uruguay
Panama
Paraguay
40.0
Chile
Trinidad & Tobago
23.8
Colombia
20.0
Guatemala
Venezuela
Brazil
0
2000
4000
6000
8000
10000
12000
GDP per capita in Constant $
14000
16000
18000
20000
2. Trend Lines
Make Sure There is a Trend on the Y Axis. Clearly Label Axes.
(Edward Tufte)
3.
Pie Charts
The First Pie Chart Ever Invented
Pie Chart Pointers
Start slices at Noon, rotate clockwise in descending order, 5 slices maximum
First
Second
Third
Fourth
Fifth
What’s the Headline?
Must be the Lake Woebegone Impact (Where Everyone is Above Average)
Is This a Good Use of Ink?
Is it the shape or the number that gives you the information?
Minimize Ink-to-Data Ratio
• Minimize the ratio of ink-to-data ratio (Edward
Tufte). Stephen Few uses ink to pixel ratio
• Data-ink ratio = data-ink/total graphic ink (the
closer to 1.0 the better)
• Some avoid the pie chart and as it often violates
Tufte’s data ink rule.
• Avoid ChartJunk, it’s all about the data.
3. Bar Charts
You eye tells the difference. Many order them by size. Avoid stacked bar charts.
4.
Area Charts
Maintain the data lie ratio, The Error of Distorting Data
Good Graphics Need Good Ideas, Not New Technology
The area is the size of Napoleon’s army marching towards and returning from Moscow.
Note the several dimensions. Is it a map or a chart? (Made in early 1800s)
Visual Maps
6. Images are One Frame Movies
7. Effective Use of Layers
8. Use Thematic Maps
9. Find Map Harmony
10. Re-Think Maps
6.
Images are One Frame Movies
Rule of the Thirds
Not Using the Rule
Using the Rule
7.
Which U.S. State Capital have the largest populations?
Hard to tell. Make Effective Use of Maps and Statistics
8.
Build Thematic Maps
Usually layers. But a single layer map can be an inferred thematic (Haiti border)
Night Pictures of Northeast Asia
A Different Way to Look at Development
9.
Find Map Harmony
How do the Color, Spaces, Data, and Point-of-View fit Together?
10.
Rethinking Maps: IPCC Climate BioRegions
There are boundaries other than state borders
Rethinking Maps
Recent Conflict History by Color Intensity (Jim Lee)
Rethinking Maps
Countries Adjusted by Population Size, http://www.worldmapper.org/
Consider New View Points
Switching Northeast and Southwest
Guidelines for Data Visualization
Integrating Visuals and Text
Attractiveness and Simplicity
Is it the Right Tool?
Discussing Visuals in the Text
a. Clearly indicate the graphic location in the
text; clearly and fully label.
b. Induce the reader to think about
substance, help access graphic
complexity, and assist in understanding a
visual idea.
c. Explain the overall dynamics that the maps
eveals. They are not static, but active
pictures.
Produce Richness, Parsimony, and Harmony in Graphics
• “To invent out of knowledge means to produce
inventions that are true. Every man [person] should
have a built-in automatic crap detector operating
inside him.” (Ernest Hemingway)
• "A sentence should contain no unnecessary words, a
paragraph no unnecessary sentences for the same
reason that a drawing should contain no unnecessary
lines and a machine no unnecessary parts.“ (Strunk
and White )
Not Everything is Useful to Graph
http://www.economistsdoitwithmodels.com/2011/03/31/graphic-content-when-bad-charts-happen-to-good-people-amazon-edition/ (Jodi Beggs)