env 20068.1 envisioning information lecture 8 – good design – what we can learn from tufte ken...
TRANSCRIPT
ENV 2006 8.1
Envisioning Information
Lecture 8 – Good Design – What we can learn from Tufte
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