Database Reference
In-Depth Information
Proximity
Things that are close together are perceptually grouped together;
Similarity
Similar elements tend to be grouped together;
Continuity
Visual elements that are smoothly connected or continuous tend
to be grouped;
Symmetry
Two symmetrically arranged visual elements are more likely to be
perceived as a whole;
Closure
A closed contour tends to be seen as an object;
Relative Size
Smaller components of a pattern tend to be perceived as objects
whereas large ones as a background.
Information Visualization experts design visual representations that try to follow
these principles. For example, graph layout algorithms such as [14] designed to
find communities in social networks adhere to the
proximity
principle by placing
nodes that are connected to a dense group close together and push away nodes
that are connected to another dense group. The Treemap algorithm [5] uses the
closure
principle to layout a tree: children of a node are placed inside their parent
node.
3 Success Stories
Information Visualization is much easier to explain using demonstrations than
words. However, to be understood, the data used should be familiar to the au-
dience and interesting. Preparing demonstrations targeted at all the possible
audiences is not possible but there are some datasets that interest most audi-
ences and greatly help make the point. Several striking static examples can be
found in Tufte's topics [24,25,26].
To better explain the value of visualization, demonstrations should start using
a simple question, show that a good representation answers the question at once
and then argue about additional benefits,
i.e.
questions the users did not knew
they had. From the users perspective, a good representation will confirm what
they already know, let them answer at once the question asked and show them
several insights, leading to the so-called “a-ha” moments when they feel like they
understand the dataset.
3.1 Striking Examples
Static examples used by most InfoVis courses include the map of Napoleon's
1812 March on Moscow drawn in 1869 by M. Minard (Figure 3) and the map of
London in 1854 overlaid with marks positioning cholera victims that led John
Snow to discovering the origin of the epidemic: infected water extracted with a
water pump at the center of the marks (Figure 4).
In general, good examples show known facts (although sometimes forgotten)
and reveal several unexpected insights at once. Minard's map can help answer the
question: “What were the casualties of Napoleon's Russian invasion in 1812?”.
The map reveals at once the magnitude of casualties (from 400,000 to 10,000
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