Paul Geladi Legacy: Pioneering Chemometrics for the Future

This special issue, entitled ‘Paul Geladi Legacy: Pioneering Chemometrics for the Future’, is a tribute to the remarkable scientific contributions of Professor Paul Geladi to the field of chemometrics. This very special issue brings together a comprehensive collection of topics that reflect the breadth and depth of Paul's work in chemometrics. While nice memories and Paul's interests in science have been shared by some of his friends and colleagues in recent publications, this editorial and its related special issue will focus on some of the most relevant scientific areas that Professor Paul Geladi explored throughout his prolific career. The title of this special issue honouring Paul is not trivial. For many years, Paul emphasized the future of chemometrics as an important and in-depth topic that should be part of scientific meetings, conferences and specialized literature. Indeed, as Paul remarked on several occasions, pioneering chemometrics for the future, not only by adapting its methodologies and advances to new challenges and technologies but also creating new chemometric research directions according to evolving trends in science, is crucial for the field of chemometrics to succeed. To achieve this, high-quality teaching and the education of the next generations in chemometrics is especially important, as well as fostering collaboration across research groups. An exemplar of the latter was the initiative led by Paul called ‘The Laboratory Profile’ (published at Journal of Chemometrics in the 90s), which strengthened the global network of chemometric laboratories and showcased the wide array of scientific activities taking place across university, research institutions and industry. The breadth of Paul's knowledge, enhanced from a rich network of scientists, enabled him to successfully apply the most suitable chemometric techniques across various applications.

Professor Paul Geladi was a dedicated educator. In 1986, when audiovisual resources were still rarely used in statistical lectures, Paul was ahead of his time publishing an article on the use of videotapes as pedagogic tools in chemometrics education. Besides, Paul wrote several tutorials on chemometric methods, two of which stand out as his most cited work. The first is his tutorial on principal component analysis (co-authored with Wold and Esbensen), which covers the most relevant aspects of PCA and its application, whilst the second tutorial focuses on partial least squares regression (co-authored with Kowalski) and covers the concept and algebra of the PLS algorithm. These tutorials published in international journals remain foundational references in the field. In addition, Paul authored three books of high relevance in the field of chemometrics. His book Multi-Way Analysis with Applications in the Chemical Sciences (co-authored with Smilde and Bro) provides chemometricians with the mathematical foundations needed to understand multi-way approaches and practically apply them. His other two books, Multivariate Image Analysis and Techniques and Applications of Hyperspectral Image Analysis (both co-authored with Grahn), have become very popular among chemometricians interested in image analysis. Analysing images was one of the main subjects of Paul's career, which is evident from the abundance of scientific articles that he authored related to multivariate and hyperspectral imaging.

Among his many contributions to method development, one of the most relevant articles written by Paul in the 80s addressed the linearization and scatter-correction for near-infrared reflectance spectra of meat (co-authored with MacDougall and Martens). Paul produced excellent publications and teaching materials related to many chemometric topics such as data pre-processing, spectroscopy (especially NIR), image analysis, multivariate calibration, multi-way analysis, variable selection, principal component analysis (PCA), partial least squares (PLS), multi-omics data analysis, machine learning, and development of chemometric algorithms. One of the main strengths of Paul was his pioneering ability to utilize and adapt chemometric methodologies to new challenges in a wide range of disciplines. To be as representative as possible of the breadth of Paul's scientific legacy, this special issue contains a selected collection of articles related to chemistry, spectroscopy, hyperspectral imaging, agricultural and food sciences, theory of sampling, environmental health, artificial intelligence, molecular biology, -omics, and development/optimization of chemometric methods.

I would like to thank all of you for your contributions and support in making this very special issue in honour of Paul at Journal of Chemometrics possible. I am sure Paul would be very happy to see so many good friends and colleagues contributing, whether through writing articles, reviewing or helping in other ways, to honour his life's work.