APPLIED MULTIVARIATE STATISTICS: WITH SAS® SOFTWARE

2.1. Introduction

Graphical techniques have become an integral part of any data analysis, especially now due to a tremendous increase in the accessibility to computing facilities. In general it is easy to use graphical methods for data with one, two, or even three variables. However, for multivariate data in dimensions higher than three, data reduction to two or three variables is needed before it is possible to plot them. Several methods to represent multivariate data are available in the literature. This chapter covers four of these methods in Sections 2.2 through 2.5. It may be mentioned that Section 2.5 may require a slightly higher level of familiarity with matrix decompositions and may be skipped at first reading. See Friendly (1991) for ...