Laboratoire des systèmes solaires (L2S). 50 av. du Lac
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S. et Aupetit, M. (2011) “CheckViz: Sanity
Check and Topological Clues for Linear and Non-Linear
30(1), pp 113-125.
scaling is a must-have tool for visual data miners, projecting
multidimensional data onto a two-dimensional plane. However, what we
see is not necessarily what we think about. In many cases, end-users do
not take care of scaling the projection space with respect to the
multidimensional space. Anyway, when using non-linear mappings, scaling
is not even possible. Yet, without scaling geometrical structures which
might appear do not make more sense than considering a random map.
Without scaling, we shall not make inference from the display back to
the multidimensional space. No clusters, no trends, no outliers, there
is nothing to infer without first quantifying the mapping quality.
Several methods to qualify mappings have been devised. Here, we propose
CheckViz, a new method belonging to the framework of Verity
Visualization. We define a two-dimensional perceptually uniform colour
coding which allows visualizing tears and false neighbourhoods, the two
elementary and complementary types of geometrical mapping distortions,
straight onto the map at the location where they occur. As examples
shall demonstrate, this visualization method is essential to help users
make sense out of the mappings and to prevent them from over
interpretations. It could be applied to check other mappings as well.