CS109 Lecture 4

CS109 Lecture 4

Visualization Goals

• Communicate (Explanatory)

  1. Present data and ideas
  2. Explain and inform
  3. Provide evidence and support
  4. Influence and persuade

• Analyze (Exploratory)

  1. Explore the data
  2. Assess a situation
  3. Determine how to proceed
  4. Decide what to do

Effective Visualization

Examples

Bikini Chart

The Obama administration released a chart a while ago that shows job losses during the last year of the Bush administration and the first year after Obama took office. The chart is simple yet effective in the way it communicates a message. It also has some very subtle design elements that communicate a much more negative undertone than is immediately obvious.

It is interesting that they chose to use bars that are pointing down rather than up. In a way, that makes sense: negative numbers typically are represented by bars that point down. But the number of people who lost their jobs is not negative, it’s only negative if you look at it as “negative job growth.” This was clearly a conscious decision. Since almost all the numbers are negative, it might have still made sense to show them pointing up though, to make the chart look less unusual. Its shape has earned the chart the nickname bikini chart, though.

The bikini chart is a great example of just how strongly simple design choices can change the appearance of a simple bar chart. Even if my speculation about weight is wrong, the other choices communicate and explain what the viewer is supposed to look for, without the need for explanatory text or a “shorter bars are better” annotation. That’s pretty good for a simple bar chart.

Visual Efficient

Visual by Data Type	Most Effective(Q/O)
Less Effective(Q/O)	Least Effective(Q/O)

Color

• Brightness [Perceived as Ordered]
• Saturation [Perceived as Ordered]
• Hue [Categories]
  
  • Do not use more than 5 - 8 colors at once

Brewer Scales

Color Blindness [Notice !]

Grouping Principles

Tips

• Clear,detailed,and thorough labeling and appropriate scales

• Size of the graphic effect should be directly proportional to the numerical quantities

• Maximiza Data-Ink Ratio

Data－Ink Ratio=Data InkTotal ink used in graphic

• Avoid Chart Junk

  extraneous visual elements that distract from the message

Effective Visualizations Tips

1. Have graphical integrity
2. Keep it simple
3. Use the right display
4. Use color strategically
5. Tell a story with data

Recommend Books