Above all else, Tufte teaches that graphics must reveal data. In The Visual Display of Quantitative Information, Tufte schools readers about graphical excellence, evidence, and integrity. He also educates the reader on what he refers to as “chartjunk”.
In order to achieve graphical excellence, a designer must be certain that graphics show the data and avoid distorting what the data have to say. Graphics should encourage the viewer to think about the substance and not about methodology, graphic design, the technology behind graphic production, or anything else.
Tufte’s principles of graphical evidence teach that graphical evidence “is the well-designed presentation of interesting data – a matter of substance, of statistics, and of design; consists of complex ideas communicated with clarity, precision and efficiency; is that which gives to the viewer the greatest number of ideas in the shortest time with the least ink in the smallest space; [and] requires telling the truth about the data.”
In relation to design and data variation, Tufte notes that every part of a graphic creates visual expectations about its other parts, and in the realm of graphical perception, these expectations very often determine what the eye sees.
This lends to Tufte’s emphasis that context is essential for graphical integrity. Graphics “must not quote data out of context.” Graphical integrity is likely to result when clear, detailed, and thorough labeling is used to overcome graphical distortion and ambiguity. Explanations of the data can and should be written out on the graphic itself, and labeling important events in the data is also recommended.
However, often times we see graphics containing what Tufte refers to as “chartjunk”. Chartjunk, or graphical decoration, is often represented as dark grid lines which can clutter up the graphic and doesn’t carry any information anyway; excess tick marks; optical art (design interactions with the physiological tremor of the human eye that can produce distracting vibrations and movement); and cross hatching often found in Excel graphs. Rather than using a cross-hatching filler, tint screens of shades of gray are recommended. Tufte tells us that if a graphic is used as a look-up table, then grid lines may be helpful in reading, but even then, the grid lines should be muted relative to the data. Color often generates a graphical puzzle, therefore, the use of refined color is suggested.
Tufte feels that “graphical decoration comes cheaper than the hard work required to produce intriguing numbers and secure evidence.” Many of those who produce graphics are trained in fine arts and have little experience with data analysis. Inept graphics thrive because many graphic artists believe that statistics are boring; they feel that they should “decorate” graphics to liven up (and all too often exaggerate) what evidence there is of the data. Unfortunately then, style replaces content.
- Tufte, Edward R. The Visual Display of Quantitative Information. 2nd Edition. Cheshire, CT: Graphics Press, 2001.