Image study of mesopotamian cylinder seals through texts: The procrustes transformation applied to correspondence analysis results

The use of Textual Correspondence Analysis to investigate a corpus of iconographic compositions carved on Mesopotamian cylinder seals proved to be very useful to understand the peculiarities of the specimens from the points of view of geographic origin, typology and inner chronology. The presence of a relatively high number of rare forms in the data set - besides the hapax - led to think, however, that the extraction of the factors - so the outcomes of the analyses - could have been influenced heavily by them. For this reason, looking for an optimal composition and for the most effective encoding of the data set, a reduction of its rarest forms was performed to find the threshold which could allow to reconcile the need for keeping the useful encoded information with the best possible reduction of elements producing high inertia. Adopting the methodology known as Procrustes, the data table was thus progressively reduced, and each time investigated: the results so obtained were then used to reach a global assessment about how much each reduced data set could correspond to the optimized one.