If there ever was a tool that could stimulate the imagination and profit from the intuition and creativity of John Tukey, it was computer graphics. John always saw graphics a being central to exploratory data analysis: "Since the aim of exploratory data analysis is to learn what seems to be, it should be no surprise that pictures play a vital role in doing it well. There is nothing better than a picture for making you think of questions your had forgotten to ask (even mentally)." Much of his work focused on static displays designed to be easily drawn by hand, but he realized that if one wanted to effectively explore multivariate data, computer graphics would be an ideal tool. PRIM-9, the first program to use interactive, dynamic graphics for viewing and dissecting multivariate data, was conceived by John during a four month visit to the Computation Research Group of the Stanford Linear Accelerator Center in early 1972. PRIM-9 opened up a fundamentally new way of exploring multivariate data. Its basic operations-Picturing, Rotation, Isolation and Masking-have stood the test of time and form the core of numerous follow-on systems. John's experiences with PRIM-9 gave rise to a slew of other ideas for the analysis of multivariate data, many of them not tied to interactive graphics. The most well known of those is "Projection Pursuit"-automatically finding interesting low-dimensional projections of multivariate data by optimizing a projection index. John was also keenly interested in ways of detecting and modeling nonlinear structures in multivariate data which might not be manifest in projections, such as concentration of data near nonlinear lower dimensional manifolds. Many of his proposals exist only in the form of handwritten notes and appear "far out" even today. John's work on Prim-9 and Projection Pursuit lent respectability to computationally oriented, non mathematical research in Statistics. He moved the center of gravity away from an (over)emphasis on mathematical theory to a greater balance between methodology, theory, and applications and thereby helped revitalize the discipline of Statistics.
