Preliminary inspection of data

In this book we place great emphasis on the visual display of the results of multivariate analysis. However, before becoming involved in more complicated analyses, we here consider some simple graphical methods suitable for a preliminary inspection of the data. These methods will often provide an insight into the data, highlighting aberrant points which may be unduly influential and allowing a check on the underlying assumptions of a proposed analysis; equally they may suggest directions for further analysis. Tukey (1977) coined the term ‘exploratory data analysis’ to describe this preliminary inspection of data. The reader will find a large number of original and ingenious graphical methods for displaying multidimensional data in Tukey and Tukey (1981) and Tufte (1983), while Green (1979) contains interesting ecological examples.