Story
- The outbreak was centred on a single water pump on Broad St.
Data Visualization
Andrew Irwin, a.irwin@dal.ca
Math & Stats, Dalhousie University
2026-01-08
Asking questions with data.
Telling stories with data.
Questions
What is the average amount of CO2 in the atmosphere?
How does this concentration change during the year? Is there a regular pattern?
How does this concentration change from one year to the next?
Stories
- CO2 in the atmosphere varies through the year, with an amplitude of about 7-9 ppm, and increases by 2-3 ppm each year.
Questions
How does this concentration change from one decade to the next?
Are the interannual patterns stable over decades?
Stories
- CO2 in the atmosphere varies regularly through the year and has increased 100 ppm over 60 years
Questions
How has this concentration changed over thousands of years?
Are current levels of atmospheric CO2 unusual?
Stories
- CO2 in the atmosphere has varied regularly from 180 to 280 ppm for hundreds of thousands of years and is now higher than it has been for 800,000 years
Questions
How has Arctic sea ice volume changed over the last few decades?
What is the regular interannual pattern of sea ice volume?
How much variation do we see year to year?
Stories
Arctic sea ice volume has shrunk by about 50% and it appears likely that the fall will be ice-free soon
Sea ice volume varies by about 15 thousand cubic km each year, with a peak in May and trough in October
Year to year variation is about 3-4 thousand cubic km, much less than the variation within a year, and about the same as the change in mean volume across a decade.
Questions
- How does fertility relate to income for different countries?
Stories
Fertility decreases as income increases, regardless of the country
The animation (or a series of stills) makes this point more convincingly
Questions
- What is the weather like in Halifax, Nova Scotia?
Story and Question
We have predictions for temperature and precipitation for the next week. The example shows the amount of variation that occurs within a day, and from day to day, in September.
What can we say about longer term patterns, averaged over many years, and displayed for all seasons?
Stories
Seasonal variation is about 24°C, daily variation is about 8°C, and year to year variation is about 7-14°C.
Questions
- What happened to Napoleon’s army in Russia in 1812?
Stories
- Napoleon’s army was reduced by about 99% over the course of the campain, largely due to cold weather and starvation.
Questions
- What caused so many deaths in the Crimean war?
Stories
- Most deaths were from preventable causes such as infectious diseases, not battle wounds.
Questions
- What caused the 1854 cholera outbreak in London?
Questions
- How did the prevelance of SARS-CoV-2 variants change over time from September 2020 to June 2022?
SARS-CoV-2 variants
Each color is a variant. Data from covariants.org
Stories
- There were at least 7 major covid variants, persisting for 4-6 months each
What is data visualization?
What is data visualization?
Turn data into images
Iterative process to explore data
Filter, summarize, and present data
What is the purpose of data visualization?
Summarize data compactly
Leverage vision machinery in brain
Helps you tell a story with data
A familiar visualization tells a story “by itself”
What makes a good visualization?
Effective communication aid
Memorable & understandable
Aesthetically pleasing - nothing confusing, jarring, or out of place
Suggested reading
Course notes: Welcome
Course notes: Invitation to Data Visualization
Wilke: Chapter 29: Telling a story and making a point
Video: Hans Rosling’s TED talk (linked in “Invitation”)
Video: Excerpt from Claus Wilke’s talk for the Santa Fe Institute (linked in “Invitation”)
Assignment 0
Prepare a short report on two visualizations you like or could improve on.
Details in Course notes (Detailed outline, Evaluation)
Submit on Brightspace, due Friday, January 23 at 11:59 PM