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

viiiPreface to the Second EditionA much shorter book on PCA (Dunteman, 1989), which is targeted atsocial scientists, has also appeared since 1986. Like the slim volume byDaultrey (1976), written mainly for geographers, it contains little technicalmaterial.The preface to the first edition noted some variations in terminology.Likewise, the notation used in the literature on PCA varies quite widely.Appendix D of Jackson (1991) provides a useful table of notation for some ofthe main quantities in PCA collected from 34 references (mainly textbookson multivariate analysis). Where possible, the current book uses notationadopted by a majority of authors where a consensus exists.To end this Preface, I include a slightly frivolous, but nevertheless interesting,aside on both the increasing popularity of PCA and on itsterminology. It was noted in the preface to the first edition that bothterms ‘principal component analysis’ and ‘principal components analysis’are widely used. I have always preferred the singular form as it is compatiblewith ‘factor analysis,’ ‘cluster analysis,’ ‘canonical correlation analysis’and so on, but had no clear idea whether the singular or plural form wasmore frequently used. A search for references to the two forms in key wordsor titles of articles using the Web of Science for the six years 1995–2000, revealedthat the number of singular to plural occurrences were, respectively,1017 to 527 in 1995–1996; 1330 to 620 in 1997–1998; and 1634 to 635 in1999–2000. Thus, there has been nearly a 50 percent increase in citationsof PCA in one form or another in that period, but most of that increasehas been in the singular form, which now accounts for 72% of occurrences.Happily, it is not necessary to change the title of this book.I. T. JolliffeApril, 2002Aberdeen, U. K.