3.9 Theory of data graphics (ToDG): Data-ink and graphical re-design

  • Large share of ink on a graphic should present data-information, the ink changing as the data change (Tufte 2001, 2:93)
  • Data-ink: Non-erasable core of a graphic, the non-redundant ink arranged in response to variation in the numbers represented (Tufte 2001, 2:93)

  • \(\text{Data-ink ratio} = \frac{\text{data-ink}}{\text{total ink used to print the graphic}}\) = proportion of a graphic’s ink devoted to the non-redundant display of data-information = 1.0 - proportion of a graphic that can be erased without loss of data-information (Tufte 2001, 2:93)

  • Rule: Maximize the data-ink ratio, within reason (Tufte 2001, 2:96)
  • Two Erasing Principles (Tufte 2001, 2:96)
    • Erase non-data-ink, within reason
    • Erase redundant data-ink, within reason


Tufte, Edward R. 2001. The Visual Display of Quantitative Information. Vol. 2. Graphics press Cheshire, CT.