Download - Practical Considerations for Displaying Quantitative Data

Practical Considerations for Displaying Quantitative Data

Cory LownNCSU Libraries

Maryland SLA21 October 2010

Outline

• History and context• Things to consider• Good questions• What is data?• What kind of chart?• Visual perception

• Data visualization tools• Where to learn more

History and context

16,500 BCE

6,200 BCE

1991 – in Maryland

Data visualization isn't new

What is new

1. Amount of data

1. Computer processing ubiquity

2. Desktop and Web applications

Computers are useless. They can only give you answers.

— Pablo Picasso

Good questions

Untitled Image Layout

• Image of something built


• Image of a tool

What is

data?

*See Stephen Few's Show Me the Numbers

155,741

155,741Searches

Quantitative information always expresses

relationships

Quantitative relationships are:

1. An association between quantitative values and categories

1. Associations among multiple sets of quantitative values

Relationships among quantities

• Nominal comparison• Time series• Ranking• Part to whole (%)• Deviation• Distribution• Correlation

What kind

of chart?

*See Stephen Few's Show Me the Numbers

Charts

• Tables

• Graphs

Tables

• Look up individual values

• Compare individual values

• Precision is important

• Multiple units of measure

A table with mixed units

Graphs

• Meaning is revealed by the shape of the values

• Show relationships among many values

1 of 13,000 pages of data

Same data in a graph

Visual

perception

*See Stephen Few's Show Me the Numbers and Christopher G. Healey's Perception in Visualization

http://www.csc.ncsu.edu/faculty/healey/PP/index.html

http://www.csc.ncsu.edu/faculty/healey/PP/index.html

Sti

mulus

Sti

mulation

Perception

Preattentive processing

Extremely fast, pre-conscious visual processing

Example

9128732198432789543287

6784905043267812837698

7843928364382398731092

3478957438298374209123

0980934591283754845645

8934678238328009748349

Some preattentive attributes

Form:• Orientation• Line length• Line width• Size• Shape• Curvature• Added marks• Enclosure

Color:• Hue• Intensity

Spatial Position:• 2D

Scatterplot

• Correlation• Nominal comparisons

Line chart

• Time series• Deviation• Distribution

Bar chart

• Nominal comparison• Ranking• Part to whole• Deviation• Distribution

Stacked bar chart

• Part to whole

The humble pie chart

Is B or C larger?

3D effects distort 2D proportions

Advice from Edward Tufte

• Show the data• Make large datasets coherent• Emphasize substance over method• Don't distort• Reveal several levels of detail• Serve a clear purpose

Data visualization tools

Google

Docs

Many

Eyes

Google

Visualization

API

Untitled Image LayoutSome JavaScript – not so bad, right?

Web tools (no coding)

• Google Docs/Gadgets* http://docs.google.com/

• Many Eyes http://manyeyes.alphaworks.ibm.com/manyeyes/

Web tools (coding)

• Google Visualization API* http://code.google.com/apis/visualization/documentation/gallery.html

• Protovis* http://vis.stanford.edu/protovis/• Flotr

http://www.solutoire.com/experiments/flotr/examples/

• Flot http://people.iola.dk/olau/flot/examples/

Web tools (coding)

• MIT Simile widgets http://www.simile-widgets.org/

• Rgraph http://www.rgraph.net/• jQuery Visualize

http://www.filamentgroup.com/lab/update_to_jquery_visualize_accessible_charts_with_html5_from_designing_with

Desktop apps (easier to use)

• OpenOffice Spreadsheet / MS Excel• Adobe Illustrator• OmniGraffle (diagramming - Mac)• Visio (diagramming – PC)

Desktop apps (harder to use)

• GraphViz (network graphs)• JMP (stats)• R (stats)• Processing* http://processing.org/

Where to learn

more

Books

• Show Me the Numbers* (Few, 2004)• Now You See It (Few, 2009)• The Visual Display of Quantitative

Information (Tufte, 1983)• Beautiful Data (Segaran

& Hammerbacher, 2009) • Visualizing Data (Fry, 2008)

Websites

• http://flowingdata.com• http://infosthetics.com/• http://www.visualcomplexity.com/vc/• http://www.gapminder.org/• http://www.visualizing.org/• http://understandinggraphics.com/

Thanks!

Cory LownDigital Technologies Development Librarian

NCSU Libraries

[email protected]