⁹ We can use measurements to create abstract maps that visualizise other useful aspects of the data, and both authors use the technique frequently when dealing with text data. Patrick has worked extensively in authorship attribution, using computational techniques to measure the “distance” between authors. MDS allows him to cluster and visualize authors and how they group based on stylistic similarity, which may or may not match similarities in genre or time. But this same type of analysis would allow historians to look at the volume of shipping between any two ports, and use this volume as a measure of how “close” they are economically. Would it be surprising to learn that colonial New York has closer economic ties to Liverpool than to colonial Savannah? And this could in fact be true, even if almost no ships sailed directly between the two, as long as (for instance) there was a lot of traffic from New York to London and from London to Liverpool ….