Jolliffe I. Principal Component Analysis (2ed., Springer, 2002)(518s)

5.2. Principal Coordinate Analysis 85Figure 5.2. Artistic qualities of painters: plot of 54 painters with respect to theirfirst two PCs. The symbol × denotes member of the ‘Venetian’ school.is looking for major directions of variation between means rather thanmajor directions of variation in a common distribution (de Falguerolles,personal communication). This view is in line with the fixed effect modelof Section 3.9, and is discussed further in Section 5.3.A variation of the simple plot of PC scores for the first two PCs isproposed by Tarpey (2000). Lines are added to the plot, correspondingto the directions of the first PC for two subsets of the data, derived bydividing the full data set according to the sign of the first PC for the wholedata set. The idea is to indicate possible non-linearity in the data (seeSection 14.1.3).5.2 Principal Coordinate AnalysisPrincipal coordinate analysis is a scaling or ordination method, sometimesknown as classical scaling. It was popularized by Gower (1966). Torgerson(1952, 1958) discussed similar ideas, but did not point out the links be-