A Grammar of Graphics

STAT 20: Introduction to Probability and Statistics

Agenda

• Concept Questions
• Lab 2: Class Survey
• Part I
• Break
• Lab 2: Class Survey
• Part II

Concept Questions

What are the aesthetics and geometry of this plot?

Answer at pollev.com

01:00

What has changed when moving from the left to the right?

01:00

You will be watching a 2.5 minute video of a presentation by a scientist, Hans Rosling, who studied global public health. He presents data visualizations depicting the change in life expectancy and family size over several decades in the 20th century.

On a piece of note paper:

• Sketch out the data frame used to create the graphic and add the names of the variables.
• List the aesthetic attributes used to encode the data in the graphic.
• Identify the geometry used in the plot.

Discuss what you came up with in terms of . . .

• the variables present in the data frame
• the aesthetic attributes used to encode that data in the plot
• the geometry
04:00

What were the variables and aesthetic attributes?

Visual Cues / Aesthetics

• Location along the x-axis
• Location along the y-axis
• Size of point
• Color of point
• Animation

Variables

• Fertility rate
• Life expectancy
• Population
• Region
• Year

What did the data frame look like?

What was the unit of observation? What were the variables? What were their type?

Unit of observation

• A country in a given year

Variables

• Fertility rate (continuous)
• Life expectancy (continuous)
• Population (continuous)
• Region (nominal)
• Year (discrete)

• Points