Displaying Quantitative Information

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# Displaying Quantitative Information - PowerPoint PPT Presentation

Displaying Quantitative Information. An exploration of Edward R. Tufte’s The Visual Display of Quantitative Information. Jeffrey Nichols Programming Usable Interfaces May 2, 2003. Good graphics. Napolean’s invasion of Russia, as drawn by Charles Joseph Minard (1781-1870).

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## PowerPoint Slideshow about 'Displaying Quantitative Information' - moshe

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Presentation Transcript

### Displaying Quantitative Information

An exploration of Edward R. Tufte’s

The Visual Display of Quantitative Information

Jeffrey Nichols

Programming Usable Interfaces

May 2, 2003

Good graphics

Napolean’s invasion of Russia, as drawn by Charles Joseph Minard (1781-1870)

More good graphics

The price of wheat compared to labour wages, William Playfair (1759-1823)

More good graphics

French train schedule, as drawn by E.J. Marey (1830-1904)

More good graphics

Map of the northern galactic hemisphere

(1.3 million galaxies shown)

How can we make better graphics?

Tufte presents some principles of data graphics

• Above all else, show the data.
• Maximize the data-ink ratio
• Erase non-data-ink
• Erase redundant data-ink
• Revise and edit
Data-Ink
• Ink that changes as the data changes
• Non-redundant ink!
Data-Ink Ratio

data-ink

Data-ink ratio =

Total ink used to print graphic

= Proportion of a graphic’s ink devoted to the non-redundant display of data-information.

= 1.0 – proportion of graphic that can be erased without the loss of information

Ratio of USA Today Graphic
• What is the data-ink ratio of this graphic?

< 0.001

How can we make better graphics?

Tufte presents some principles of data graphics

• Above all else, show the data.
• Maximize the data-ink ratio
• Within reason
• Every bit of ink on a graphic requires a reason
• Erase non-data-ink
• Erase redundant data-ink
• Revise and edit
How can we make better graphics?

Tufte presents some principles of data graphics

• Above all else, show the data.
• Maximize the data-ink ratio
• Erase non-data-ink
• Erase redundant data-ink
• Revise and edit
Erase non-data-ink, within reason

11

5

2

1

0

18

7

Histogram of Midterm Results

# of Students

A-

B+

A

B

B-

C

Scoring Buckets

Erase redundant data-ink

11

5

2

1

0

18

7

Histogram of Midterm Results

# of Students

A-

B+

A

B

B-

C

Scoring Buckets

Erase redundant data-ink

18

11

5

2

1

0

7

Histogram of Midterm Results

What’s the data-ink ratio?

# of Students

A-

B+

A

B

B-

C

Scoring Buckets

How can we make better graphics?

Tufte presents some principles of data graphics

• Above all else, show the data.
• Maximize the data-ink ratio
• Erase non-data-ink
• Erase redundant data-ink
• Revise and edit
The Principles Applied to Common Forms

Box Plots

Maximum

75%

Median

25%

Minimum

The Principles Applied to Common Forms

Box Plots

Maximum

75%

Median

25%

Minimum

The Principles Applied to Common Forms

Bar Graphs

Modified Graph

Original Graph

The Principles Applied to Common Forms

Scatter Plots

Modified Graph

Original Graph

The Principles Applied to Common Forms

Another Scatter Plot Variant

Conclusions
• Show data variation, not design variation
• Avoid using ink for non-data items
• Avoid redundancy
• Clear and detailed labeling should be used to defeat graphical distortion
• Revise and Edit

### Thanks for a great class!

Reminder:

Final Exam on Friday, May 9th at 8:30am in this room

Tufte’s Principles
• Graphical Integrity
• The representation of numbers, as physically measured on the surface of the graphic itself, should be directly proportional to the numerical quantities represented.
• Clear, detailed, and thorough labeling should be used to defeat graphical distortion and ambiguity. Write out explanations of the data on the graphic itself. Label important events in the data.
• Show data variation, not design variation.
• In time-series displays of money, deflated and standardized units of monetary measurement are nearly always better than nominal units.
• The number of information-carrying (variable) dimensions depicted should not exceed the number of dimensions in the data.
• Graphics must not quote the data out of context.
• Theory of Data Graphics
• Above all else, show the data.
• Maximize the data-ink ratio
• Erase non-data-ink
• Erase redundant data-ink
• Revise and edit