Chemometrics 1971-2011, memories and reflections.

The period 1965 to 1990 saw a dramatic change in Chemistry, from ”wet” to instrument based ”electronic” Chemistry. The former was based on weighing and titration for quantitative results, and reagents and indicators for qualitative information. The latter uses instrumentation such as chromatographs and spectrometers providing quantitative data about samples and reactions, but no immediate information. Computerized data analysis was now needed for the conversion of the data to interpretable results, and the emerging field of ”chemical data analysis” was called ”Chemometrics” in analogy to Biometrics, Econometrics, Psychometrics, etc. In its infancy, Chemometrics was focussed on classification (”supervised pattern recognition”) and the graphical overview of data, but gradually quantitative relationships such as multiple regression were becoming the dominating interest (including graphical aspects thereof). Chemical data sets often have many variables and rather few observations (cases, samples), which made existing data analytical and statistical methods difficult to apply without recourse to mutilating variable selection. Approaches for the analysis of data sets with many variables and few observations were clearly needed. Against everybody’s advice, such approaches were developed in Chemometrics, first for classification (the SIMCA method and similar), and thereafter for regression problems (PLS-regression and extensions). The development continued in various directions, particularly towards interesting applications in biology and engineering, and the interpretability of resulting models, so that today Chemometrics provides a fairly adequate data analytical toolbox covering common applications of ”chemical data analysis”. Thinking back at these happy years, I try to contemplate what we may learn from this development, and of course I become distracted by sentimental memories of funny moments, good friends, and unexpected revelations. The talk provides some glimpses thereof, as well as some reflections on possible cross-fertilizations between the ”multi-block PLS” and the Chemometrics communities.