Graphical Display and Presentation of Quantitative Information 13 February 2006

What goes into making a good figure? Based on the work of Edward R. Tufte, The Visual Display of Quantitative Information “At their best, graphics are instruments for reasoning about quantitative information” Napoleon’s Russian campaign, shown by C. J. Minard

Graphical Excellence Basic philosophy: Assume your audience is intelligent Developing an excellent graphic takes hard work Most graphs, like many other endeavors follow the Rule: You can get it 80% done with 20% of the effort, but the remaining 20% is hard work, and takes the remaining 80% of the effort.

Clarify by adding more detail, not less

Plots should be data-rich Maximize data-ink Data Density = (no. of entries in data matrix)/(area of graphic) Data Ink Ratio = (data-ink)/(total ink in the plot) Use multiples for comparisons Visual metaphors can be useful Avoid pie-charts -- they are low in data density and do not order data along a visual dimension

Trellis diagram showing barley production at different sites for two years (1931 and 1932) The data are the yields for all combinations of site, variety, and year Small multiples are inevitably comparative

Avoid chart junk Chart elements in close proximity create a visual interaction (1+1=3) Avoid using moiré patterns, optical vibration (e.g. cross- hatching)

Where possible, use direct labelling instead of legends Use horizontal text Avoid abbreviations

Present Real Data Visual metaphors are helpful too

The Lie Factor "The representation of numbers, as physically measured on the surface of the graphic itself, should be directly proportional to the quantities represented."

Plots should be: Comparative Multivariate High density Able to reveal interactions, comparisons, etc And where nearly all of the ink is actual data ink Small multiples can be visually effective

/Example of a good poster

Ask the right questions 1.Does the display tell the truth? 2.Is the representation accurate? 3.Are the data documented? 4.Do the display methods tell the truth? 5.Are appropriate comparisons, contrasts, and contexts shown?

Slideware is Evil “Power corrupts, PowerPoint corrupts absolutely” (Tufte, 2003) Presentations should serve the audience, not the speaker It should supplement the presentation, not be the presentation

Some tips Maintain high data density without excessive text Do not abbreviate statements to the point that they don’t make sense Bullet lists do not explain multi- dimensional relationships so try to use graphics Do not use the AutoContent Wizard!

If Abe Lincoln had had Power Point:

Designing Scientific Posters The poster is a large document, not just decorative It contains an Introduction that motivates the reader to continue. List the research objectives Figures are large and clearly labeled State your conclusion and be sure they are tied to the objectives References Acknowledgements The Methodology section should be short but contain sufficient detail Use graphics to show your Results

Making your poster presentation matter Make the title both informational and interesting Use color and symmetry to make your poster beautiful Someone should be able to read the entire poster in less than 10 minutes Develop your “elevator speech” No text smaller than 24 point

More tips The printed version may look different from the computer screen version Computer graphics use color additive process (RGB) whereas printers use a color subtractive process (CMYK) Printers don’t have as many color combinations as computers Avoid using saturated colors Avoid using low-resolution graphics

Your professional demeanor No gum Avoid annoying mannerisms Dress appropriately Show up! Look at your audience when you are speaking, thank them, shake hands Provide letter-sized color copies Bring business cards Follow up on requests for information