# Summary of Edward Tufte's Visualization Course

ddgarcia@cs.berkeley.edu

## Overview

I attended a one-day course titled Envisioning Data and Information taught by Edward Tufte in the Fall of 1994 and I thought I'd highlight the main topics presented. If you'd like to find out more about these issues, please see me in person.

## Basic Problem

### Multi-variate data

Everything interesting we want to display is a multi-variate (multi-variable) problem and all we can use is a 2-D space

## Small Multiples

There is an inherent problem when displaying similar images (e.g. frames from an animation) on separate pages, forcing the reader to flip back and forth to compare the nth frame to the n+mth frame known as the one damned thing after another problem. It is solved by displaying many small multiples at once. Small multiples are small, thumbnail-sized representations of the images displayed all at once, which allows the reader to immediately, and in parallel, compare the inter-frame differences.

## Smallest Effective Difference

Whenever you make a mark (label, line, etc.), make it as small as possible, but as small as possible to still be clear. This enhances the resolution.

## Causality (Answering the question: "Compared to What?")

Displays should show causality of the various parameters. The correlation of the presence of the cause -> presence of the effect and absence of the cause -> absence of the effect should be investigatable.

## Context

Data should be put in proper context. Example: "I just got a raise of \$1000 this year" tells us nothing. How does that compare to what you were making last year? How does that compare to raises in the past? How does your % raise compare to others in the company? How does it compare to others at other companies doing your same job?

## References

Tufte, Edward R. The Visual Display of Quantitative Information, Graphics Press, Cheshire, CT 1983.

Tufte, Edward R. Envisioning Information, Graphics Press, Cheshire, CT 1991.

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