1. ENV 20068.1 Envisioning Information Lecture 8 – Good Design – What we can learn from Tufte Ken Brodlie kwb@comp.leeds.ac.uk

2. ENV 20068.2 Tufte Design Principles Give the viewer the greatest number of ideas in the shortest space of time using the least ink in the smallest space Try to maximize the data-ink ratio Try to maximize the data density Show data variation, not design variation Tell the truth about the data

3. ENV 20068.3 Data Ink Data Ink Ratio = (data-ink) / (total ink to produce graphic) = proportion of ink devoted to non- redundant display of information = 1.0 – proportion of graphic that can be deleted without loss of data-information A low value of data ink ratio!

4. ENV 20068.4 Exercise How much can be removed from this graphic? –1 –2 –3 –4 –5 –6 Answer at: http://home.ched.coventry.ac.uk/Volume/vol0/dataink.htm

5. ENV 20068.5 Box Plots Even well established techniques can be improved How can a box plot be improved in terms of its data ink ratio?

6. ENV 20068.6 Scatter Plots How can we improve the data ink ratio for the scatter plot?

7. ENV 20068.7 Tuftes Range Frame 6

8. ENV 20068.8 BCS Yearbook 2006 BCS Yearbook contains this diagram… How would you draw this graphic?

9. ENV 20068.9 Data Density Data density = (number of entries in data matrix) / (size of graph) Low data density!

10. ENV 20068.10 Exercise Calculate the data density for these two examples –Suppose area is 10 sq units of area Gender, height and weight recorded for 92 students –Density for gender breakdown = –Density for height-weight relationship =

11. ENV 20068.11 Design Variation Fundamental purpose of a graph is to show changes in the data Design variation – where the same data is displayed differently for decoration - is to be avoided Leads to ambiguity and deception What is wrong with this?

12. ENV 20068.12 Lie Factor = (Size of effect on graph) / (Size of effect on data) Spot the lie!

13. ENV 20068.13 Exercise What is the lie factor in this graphic?

14. ENV 20068.14 Reflection.. But it is not an easy matter Consider this graphic –Rate it for data ink, data density and lie factor Discuss!

15. ENV 20068.15 Show the Context Remember that integrity is important in data presentation Consider the graph opposite –Conclusions can be very different depending on what is shown Spanish alcohol consumption

16. ENV 20068.16 Acknowledgements This work is largely inspired by ET – Edward Tufte Thanks to the following web sites: –http://www.infovis.net/printMag.php?num=109&lang=2http://www.infovis.net/printMag.php?num=109&lang=2 –http://home.ched.coventry.ac.uk/Volume/vol0/philosop.htm