Page 6 - Jolliffe I. Principal Component Analysis

Preface to the Second Edition

Since the first edition of the book was published, a great deal of new ma-
terial on principal component analysis (PCA) and related topics has been
published, and the time is now ripe for a new edition. Although the size of
the book has nearly doubled, there are only two additional chapters. All
the chapters in the first edition have been preserved, although two have
been renumbered. All have been updated, some extensively. In this updat-
ing process I have endeavoured to be as comprehensive as possible. This
is reflected in the number of new references, which substantially exceeds
those in the first edition. Given the range of areas in which PCA is used,
it is certain that I have missed some topics, and my coverage of others will
be too brief for the taste of some readers. The choice of which new topics
to emphasize is inevitably a personal one, reflecting my own interests and
biases. In particular, atmospheric science is a rich source of both applica-
tions and methodological developments, but its large contribution to the
new material is partly due to my long-standing links with the area, and not
because of a lack of interesting developments and examples in other fields.
For example, there are large literatures in psychometrics, chemometrics
and computer science that are only partially represented. Due to consid-
erations of space, not everything could be included. The main changes are
now described.
Chapters 1 to 4 describing the basic theory and providing a set of exam-
ples are the least changed. It would have been possible to substitute more
recent examples for those of Chapter 4, but as the present ones give nice
illustrations of the various aspects of PCA, there was no good reason to do
so. One of these examples has been moved to Chapter 1. One extra prop-