Multifunctioning Graphical Elements

Source: The Visual Display of Quantitative Information (VDQI), 1983 / 2nd ed. 2001. The named design forms are introduced in Chapter 6, "Data-Ink Maximization and Graphical Design" (pp. 123–137), and the unifying principle in Chapter 7, "Multifunctioning Graphical Elements" (pp. 139–159), 2nd ed.

Verification note: page citations below are verified against the 2nd ed. (2001). One figure from a prior draft — a "~87% ink reduction" — remains unverifiable and stays out; the closest published figures are the 80→10 straightedge economics (p. 125) and the 65%-erased bar chart (p. 101).

Overview

The same ink should usually do more than one job. A single graphical element can carry data and perform a design function normally handed to non-data-ink, or it can encode several variables at once. Designed with care, these multifunctioning elements pack complex, multivariate data into a small, legible space; designed carelessly, they collapse into puzzles only their inventor can read. The standard rectangular frame is the prime target: it does exactly two jobs — separating the data and grid from the surrounding labels, and hanging the tick marks (p. 139) — which is why it is the prime candidate for mobilization.

"Mobilize every graphical element, perhaps several times over, to show the data." — Tufte, VDQI, Ch. 7

§1. Data Measures Built From the Data

The data measure is the ink that actually locates or plots the value. When the data measure is built out of the data itself, the graphic gains quantitative detail and dimensions at no extra ink cost. Tukey's rule, as Tufte adopts it: if a mark must be made, make it carry meaning, and the simplest meaningful mark is a digit.