Mapping Associations - Mapping Scientific Frontiers: The Quest for Knowledge Visualization - page 118

Fig. 3.28 An MDS configuration of the 406 cars in the CRCARS data, including an MST overlay.
The edge connecting a pair of cars is coded in grayscale to indicate the strength of similarity: the
darker, the stronger the similarity. The MST structure provides a reference framework for assessing
the accuracy of the MDS configuration (Courtesy of http://www.pavis.org/ )
Fig. 3.29 The procedure of
journal co-citation analysis
described in Morris and
McCain ( 1998 )
Kruskal and Wish ( 1978 ) suggested that a two-dimensional MDS configuration
is far more useful as a base map than a three-dimensional one. In MDS, the overall
fitness between the similarity data and a spatial configuration is measured by a
stress value. In general, the lower the stress, the better the fit is. However, the stress
value is not the only criterion. A pragmatic rule is to look at the overall clarity and
simplicity of the map and then decide whether the layout is good enough at the
present stress level. The computational cost of reducing the stress value tends to