Shall we use range frames?

Tufte points out that the “frame of a graphic can become an effective data-communicating element simply by erasing part of it.*” There is no need to start your vertical axis at zero if your smallest value is 13, for instance. On the other hand, starting the axis with a tick mark labeled 13 gives the reader an additional piece of information that is only possible by extrapolation and visual estimation if the graph is designed in Excel. The same applies for the maximum value and the upper limit of the axis. See Figure 1 below for an example.

When the data are magnitudes, it is helpful to have zero included in the scale so we can see its value relative to the value of data. But the need for zero is not so compelling that we should allow its inclusion to ruin the resolution of the data on the graph. There has been much polemical writing about including zero when graphs are used to communicate quantitative information to others. Too frequently zero has been endowed with an importance it does not have. Darrel Huff in his book How to Lie with Statistics goes so far as to say that a graph magnitudes without a zero line is dishonest**. Read more about range frames and how to create them in the booklet Data Visualization!


*Read on range frames in The Visual Display of Quantitative Information, 2nd edition by E. Tufte, Cheshire, Connecticut: Graphics Press. 2001. ISBN-13: 978-0961392147

** Cleveland,W.S.: The Elements of Graphing Data. Wadsworth & Brooks/Cole Advanced Books & Software. Pacific Grove, CA, 1985, p. 68-89