Graphical introduction to principal components analysis

Principal components analysis (PCA) is probably the most widely used and best known chemometric (or indeed multivariate) technique. A few, out of many, representative articles provide more in-depth discussion for interested readers.1–4 We have published more than 30 articles for more than 5 years in the current series, but without yet mentioning PCA. The next articles will introduce this technique from a variety of viewpoints.