Ideal Point Discriminant Analysis Revisited with a Special Emphasis on Visualization

Ideal point discriminant analysis is a classification tool which uses highly intuitive multidimensional scaling procedures. However, in the last paper, Takane wrote about it. He concludes that the interpretation is rather intricate and calls that a weakness of the model. We summarize the conditions that provide an easy interpretation and show that in maximum dimensionality they can be obtained without any loss. For reduced dimensionality, it is conjectured that loss is minor which is examined using several data sets. This research was conducted while the author was sponsored by the Netherlands Organisation for Scientific Research (NWO), Innovational Grant, no. 452-06-002.