STANDARDIZATION AND TRANSFORMATION IN PRINCIPAL COMPONENT ANALYSIS, WITH APPLICATIONS TO ARCHAEOMETRY

Principal component analysis is commonly used in archaeometric applications to identify or display structure in the chemical composition of archaeological artefacts. A recurring topic of debate is whether, and how, data should be transformed and whether. after transformation, standardization should be used. Most discussion has focused on the use of logarithmic transformations. The merits of different approaches are investigated empirically in the paper, using 20 published data sets showing different degrees of structure. The opportunity is taken to examine the merits of the rarely used rank transformation, which has potential attractions when outliers occur or the variables are unusually distributed.