Courses/Computer Science/CPSC 203/CPSC 203 2008Winter L03/CPSC 203 2008Winter L03 Lectures/Lecture 8

Lecture 8
Today we recap the visual introduction to basic statistical concepts from the last lecture, then focus on developing some principles around the visual display of information, based on the history of charting.


 * House Keeping
 *  MIDTERM: Tuesday February 26th  -- Note I'll post some practice questions to BB next week.
 * PREREADING: Chapter 11: Databases and Information Systems to prepare for next week
 * Participatory Excercises and Peer Review
 * No office hour Thursday Feb 7th(today) -- re-schedule for next tuesday.
 * Assignment 1 will be introduced on Tuesday (data set introduced today)


 * Todays Topics
 * Quick Recap of Visual Intro to Stats
 * Principles for the Visual Display of Quantitative Information.

Lecture Glossary

 * Classification (added to Lecture 7 Glossary)
 * Data Ink (see below)
 * Chart Junk (see below)

Some Landmark Folk in the Visual Display of Quantitative Information

 * William Playfair --- http://en.wikipedia.org/wiki/William_Playfair
 * Scottish Engineer and Political economist late i8th century
 * Gathered, and improved many of the common visual patterns of his day and essentially created the field of "information Graphics".
 * Incorporated principles from ART -- e.g. Golden Ration.


 * John Tukey -- http://en.wikipedia.org/wiki/John_W._Tukey
 * 20th century statistician/mathematician
 * essentially distinguished "Confirmatory" and "Exploratory" statistics.
 * Confirmatory statistics tests hypotheses; whereas Exploratory statistics generates hypotheses by looking for pattern and structure in data.
 * emphasized graphic methods are importent for genration hypotheses, and developed a number of graphical techniques.
 * with colleagues, looked both created new data graphics, and revised many existing data graphics.


 * Edward Tufte -- http://en.wikipedia.org/wiki/Edward_Tufte
 * Key modern proponent of good graphic design in the visual display of information.
 * Integrated both the older work of Playfair and newer work by Tukey and colleagues in exploratory data analysis to define a small set of principles for the visual display of information

Visual Display of Information
Two Critical Principles in the Visual Display of Information are:
 * Statistical Accuracy (the numbers are the "right" numbers, correctly calculated given the data population/sample you are using).
 * Cognitive Effect (the pattern in the data is made clear as possible to the viewer).

Design Issues in the Visual Display of Information (or the World According to Tufte)
 * 1) Maximize Data Ink -- Ink that directly conveys information about data points
 * 2) Minimize Chart Junk -- All additional glyphs, bells, whistles, 3D effects that do not directly convey data information.
 * 3) Use Small Multiples to deal with Complexity -- Create a basis for comparison in large or complex data sets by creating simple diagrams with common axes or common design elements. Example: http://en.wikipedia.org/wiki/Small_multiple
 * 4) Data Density -- Very large data sets or very complex data sets require us to find visual techniques that maintain the content of the data, but allow us to get a "gestalt" view that can not be obtained from reading a massive data table.
 * 5) Multiple Use -- If possible put visual elements to multiple uses. Data points, could also be numbers reflecting data values. Data glyphs could reflect relationships between the data attributes in frame, and other data attributes.
 * 6) Aesthetics -- The same principles that make various art constructs effective apply also to visualization of data. Example -- use of the "Golden Rectangle" for 2 D displays. http://en.wikipedia.org/wiki/Golden_rectangle

Bad Chart Examples
http://j-walkblog.com/index.php?/weblog/posts/bad_charts/

http://lilt.ilstu.edu/gmklass/pos138/datadisplay/badchart.htm

Good Chart Examples
http://lilt.ilstu.edu/gmklass/pos138/datadisplay/sections/goodcharts.htm

http://www.compassgr.com/sites/mark/index.htm

Information Dashboard
 "Visual Display

 of the most important information needed to achieve one or more objectives 

 which fits entirely on a single computer screen 

 so it can be monitored at a glance 

.... Stephen Few

Few's 13 Mistakes in Dashboard Design

 * Exceeding the Boundaries of a Single Screen
 * Supplying Inadequate Context for the Data
 * Displaying Excessive Detail or Precision
 * Choosing a Deficient Measure
 * Choosing an Inapropriate Display Media
 * Introducing Meaningless Variety
 * Using Poorly Designed Display Media
 * Encoding Quantitiative Data Innacurately
 * Arranging the Data Poorly
 * Highlighting Important Data Innefectively or Not at All
 * Cluttering the Display with Useless Decoration
 * Misusing or Overusing Color
 * Designing an Unattractive Visual Display

.... If you understand the 6 principles of Visual Display of Information .... you are much less likely to make these 13 mistakes.

Next Class -- we will introduce some of the "cognitive rules" that govern the limits of human visual perception -- i.e. the limits of our ability to discriminate using visual clues. We will also go in detail through the "Who Are We" survey data set.

Resources
The Visual Display of Quantitiative Information. 1983. By Edward R. Tufte. See also the Tufte Web Site http://www.edwardtufte.com/tufte/

A good article on Tufte appears in the online magazine, Salon, at http://www.salon.com/march97/tufte970310.html

The Elements of Graphing Data. 1985. By William S. Cleveland.

Information Dashboard Design. The Effective Visual Communication of Data. 2006. By Stephen Few.