The Functional Art is perhaps the starting place for learning the main principles of visualising information in the media. Cario, an experienced data journalist and professor at the University of Miami, takes the reader through the basic principles of data journalism, discussing the what, why, and how of creating arresting and valuable information visualisations. The book was published in 2013, so there are many reviews that discuss the work on its merits already. I do not want to replicate that. What I want to do here, is think about some of the ways in which Cario’s book, and the kinds of visualisations it advocates, might benefit historians and historical work, and where questions and issues remain.

Cario’s main principle is that good information visualisations do not simply show or illustrate, they inform and enable exploration. As he puts it, “Graphics, charts, and maps aren’t just tools to be seen, but to be read and scrutinized” (Cario 2013, xx). This is obviously a useful principle for academic work both within the academy and in public facing works too. But the practicalities are not straightforward. Whilst historians are certainly used to forming and writing compelling and necessarily streamlined narratives and arguments from the messiness of manuscripts, archival documents, and the like, there is nevertheless room to incorporate that messiness as part of the text. This works to enrichen and deepen the work. How to do so with data?

For data visualisations, the answer seems to be creating series of visualisations, where the narrative or argument made is not linked to any single part of the visualisation, but relevant to all of them. Cario sprinkles examples of such infographics throughout the book – see one of his (and my) favourites below, ‘Driving Shifts into Reverse’ by Hannah Fairfield for the New York Times. The main graph, a connected scatterplot which itself takes some reading, is supported by a number of smaller versions of it which highlight important historical trends or events relevant to the overall argument. The result is that the graph not only illustrates the historical trend in an arresting form that benefits engagement by the reader, depth is given to that trend through the author’s provision of further annotations on the graph. The presentation encourages and enables the reader to engage in detail with the graph, in part due to its relative complexity.

But as historians, how do we get to this point? That is much trickier. Cario, understandably, largely assumes that mostly reliable data is quickly and readily available, but this might not be the case for historians. In my work as Research Assistant on the ‘Networks, Books and Markets: Using Visualisations to Explore Early Scottish Auction Catalogues’ project, a large part of my job has simply been transcription – gradually entering in titles of books sold at Scottish auctions into a database that, when big enough, can be used to quantify the trade in books at auction in the period of our research (1686–1760). It will be reliable but is also quite an investment in time and resources. Quicker methods, however, raise other problems. For instance, it is estimated that the OCR (optical character recognition) software used to render all text in the works on the Eighteenth-Century Collections Online database searchable is 90% accurate. That sounds fantastic of course, but that level of inaccuracy might skew results. As Jacob Heil and Todd Samuelson put it: “Incomplete and inaccurate metadata and bad OCR results—both of which can be found in Google Books’ early English offerings—can lead to arguments that ultimately are untenable” (Heil and Samuelson 2013, 95). Then there’s the problem that even when we do get some kind of useable data, what we do it to make it presentable necessarily involves some kind of smoothing out of the data so that its noisiness does not obscure the point made.

There are, of course, opportunities for historians in all of this. In a public engagement context we might, for example, make explicit how data was gathered and discuss what the issues might be in representing that data in various ways. Moreover, we have opportunities not necessarily present in the media context that Cario works in. One omission from his work that I found surprising in The Functional Art was any explicit discussion of accessibility. There were some implicit points – for instance, when discussing colour in infographics, it was naturally advised to avoid palettes that colour-blind people would struggle with. But the overall impression was that the imagined audience for such work was an affluent, broadsheet newspaper and high-brow magazine reading audience who had time to study the graphics. That makes sense of course – it seems to be the context in which Cario was working. But historians have opportunities to engage with diverse audiences outside of the bounds of paid, printed publications or websites that require good processing power and internet connections of their users: what can we do then?

One more lesson from Cario’s book provides a salient point. The book itself emphasises the difficulty of transferring between different kinds of media. Most of the visualisations look good, but those that were originally published as large, double-page spreads in broadsheet newspapers become fiddly in smaller form, with teeny illustrations and crowding graphs. Similarly, the representations of dynamic, online interactive graphics do not transfer particularly well to the page. There is a DVD intended to come with the book, but unfortunately this was missing in the copy that I borrowed (there is a lesson in the difficulty of preserving the digital in this anecdote somewhere!). In other words, function and form need to be considered alongside one another: when is it appropriate to use infographics in historical research and in what journals? When are interactive graphics the best way of engaging audiences online?

To conclude, The Functioning Art is simply a must to begin with the visualisation of information. But from there, historians will encounter different issues and opportunities. That throws up lots of room for exploration and experimentation in visualising history.