tufte-data-densitylisted

# Data Density and the Size of the Data Matrix ## Overview The chapter's title names two co-equal quantities, not one: the **density** of a graphic (data per unit area) and the **size of its data matrix** (total data the graphic carries). Tufte's empirical finding, from sampling published graphics circa 1979-1980, is that most graphics fail on both — the average published graphic shows about 50 numbers at roughly 10 per square inch, when the printed medium supports thousands per square inch and matrices in the thousands. High density is not clutter: clutter is non-data-ink competing for space; high density is data-ink filling it. The two require opposite remedies, and the governing instruction is to push both quantities up together. Source: *The Visual Display of Quantitative Information*, Chapter 8, "Data Density and Small Multiples," pp.161-176; Chapter 7, "Multifunctioning Graphical Elements," pp.139-159. ## §1. The Two Formulas The chapter measures two distinct things. Treat them as separate axes — a graphic can be high on one and low on the other. **1. Data density** = number of entries in the data matrix / area of the data graphic Area in square inches (or square centimeters). Answers: *how concentrated is the information?* **2. Size of the data matrix** = total number of entries (rows × columns of values) the graphic displays Answers: *how much information is there at all?* A small, sparse table plotted at large size is low on both. Shrinking it raises density b