Ink is a project that aimed at better understanding how data visualization can support (digital) Humanities research. In particular, it has been developed for the exploration of correspondence data, through a combination of three interrelated visualizations.
Ink is a web tool conceived and designed as part of my PhD research, during my visiting appointment at Stanford University in Spring 2011, within the Stanford Humanities Center and in collaboration with the Mapping the Republic of Letters project.
The first visualziation is a map showing the path (origin/destination) of the letters. Letters' paths are represented by curves that connect the coordinates of the places (mostly cities). The angle of the curve conveys the direction of the letters, while the thickness represents the number of letters exchanged between the two places.
The second visualizations is a stacked bar chart that groups letters by year. Each year is a stacked bar, showing the composition of the letters according to a criteria/dimension. By default, the chart shows the number of letters that can be plotted, that are the ones for which origin and destination coordinates have been retrieved. This view has been specifically designed in order to convey the idea of the small number of letters for which is possible to know the exact location of the places they have been shipped and received.
The third visualization is an alluvial (or Sankey) diagram (see Fineo project for more information). In this case, the diagrams presented a fixed and predetermined sequence of axes. Gender, nationality and milieu have been chosen as the default dimensions for the diagram.
You can try a demo of the tool with Voltaire's Correspondence data by the Electronic Enlightenment Project and Prof. Dan Edelstein (French and Italian, Stanford University).