A Grammar of Graphics

STAT 20: Introduction to Probability and Statistics

Agenda

  • Announcements
  • Concept Question
  • Concept Activity
  • Quiz Review
  • Break
  • Lab 2.2: Computing on the Data

Announcements

  • Quiz 1 is not this upcoming Monday, but next Monday(2/12) in-class. This Monday will be a workshop to complete Lab 2 and PS 4.
  • Lab 2 (both parts) due Tuesday Feb 13 at 9am.
  • Problem Set 4 due Tuesday Feb 13 at 9am.
  • Two problem sets without numbers relating to the Understanding the World with Data and A Grammar of Graphics will be posted to the resources tab on the home page of the course website. These are not for a grade and are for studying purposes.
  • Quiz 1 on Monday Feb 12, in class.
    • Individual portion [25 minutes]
    • Group (max. 3) portion [15 minutes]
    • Please consult the Quiz Megathread and Syllabus for content and logistical questions.

Concept Question

What code was used to make the following plot?

  • Choose an answer at pollev.com.

Concept Activity

Concept Activity

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.

Please turn to your neighbors and…

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)

What geometry is used to represent the observations?

  • Points

Quiz Review

  • Head to pollev.com for a series of former quiz questions and quiz-level questions! Make sure you take notes.

What type of claim was made?

01:00

What type of variable is listeners?

01:00

What type of proportion is used?

Roughly 68 percent of those passengers who were in the first class survived the wreckage of the Titanic.

01:00

Which measure of center/spread is least appropriate?

01:00

What are the aesthetics and geometry of this plot?

01:00

What has not changed when moving from left to right?

Break

05:00

Lab 2.2: Flights

40:00

End of Lecture