ENV 2006 8.1

Envisioning Information

Lecture 8 – Good Design – What we can learn from Tufte

Ken Brodliekwb@comp.leeds.ac.uk

ENV 2006 8.2

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

ENV 2006 8.3

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!

ENV 2006 8.4

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

ENV 2006 8.5

Box Plots

• Even well established techniques can be improved

• How can a box plot be improved in terms of its data ink ratio?

ENV 2006 8.6

Scatter Plots

• How can we improve the data ink ratio for the scatter plot?

ENV 2006 8.7

Tufte’s Range Frame

6

ENV 2006 8.8

BCS Yearbook 2006

• BCS Yearbook contains this diagram…

• How would you draw this graphic?

ENV 2006 8.9

Data Density

• Data density

= (number of entries in data matrix) / (size of graph)

Low data density!

ENV 2006 8.10

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 =

ENV 2006 8.11

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?

ENV 2006 8.12

Lie Factor

• Lie Factor

= (Size of effect on graph) / (Size of effect on data)

Spot the lie!

ENV 2006 8.13

Exercise

• What is the lie factor in this graphic?

ENV 2006 8.14

Reflection

• .. But it is not an easy matter

• Consider this graphic– Rate it for data ink, data density

and lie factor

• Discuss!

ENV 2006 8.15

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

ENV 2006 8.16

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=2

– http://home.ched.coventry.ac.uk/Volume/vol0/philosop.htm