# 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.

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

# 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

# Break

05:00

# Lab 2.2: Flights

40:00