If I may go retro, I came across the concept of Isotype charts a few years ago ago and I think it's useful to look back nearly a century to early data graphics. "The Transformer" (Hyphen Press, London, 2007) looks at the work of Otto Neurath and his associates and later wife, Marie. The basic concept was putting information into visual form. Though they weren't approaching the idea from the perspective of journalism, it is directly applicable.
"From the data given in words and figures a way has to be found to extract the essential facts and put them into picture form. It is the responsibility of the 'transformer' to understand the data, to get all necessary information from the expert, to decide what is worth transmitting to the public, how to make it understandable, how to link it with general knowledge or with information already given in other charts. In this sense, the transformer is the trustee of the public." - Marie Neurath
