Leland Wilkinson’s The Grammar of Graphics is a classic in the data visualization literature. Wilkinson created a framework that coherently ties together many aspects of designing, implementing, reading, and understanding a graphic. It’s a useful approach and has been fairly influential: The popular R package
ggplot2 is, more or less, an implementation of Wilkinson’s ideas, and I also see their influence in the software Tableau (about which more another time). Wilkinson himself helped to build these ideas into SPSS’s Graphics Production Language (GPL) and then SPSS Visualization Designer.
So what’s so special here? One of the core ideas is to start with the raw data and think about all the transformations, summaries, etc. that go into graphing it. With a good framework, this can help us see connections between different graphs and create new ones. (The opposite extreme is a “typology” or list of graph types, like you get in Excel: do you want a bar chart, a pie chart, a line chart, or one of these other 10 types? Such a list has no deep structure.) Following Wilkinson’s approach, you’ll realize that a pie chart is basically just a stacked bar chart plotted in polar coordinates, with bar height mapped to pie-slice angle… and that can get you thinking: What if I mapped bar height to radius, not angle? What if I added a variable and moved to spherical coordinates? What if I put a scatterplot in polar coordinates too? These may turn out to be bad ideas, but at least you’re thinking — in a way that is not encouraged by Excel’s list of 10 graph types.
This is NOT the approach that Wilkinson takes.
But, of course, thinking is hard, and so is this book. Reading The Grammar of Graphics requires much more of a dedicated slog than, say, Edward Tufte’s books, which you can just flip through randomly for inspiration and bite-sized nuggets of wisdom. (I admire Tufte too, but I have to admit that Wilkinson’s occasional jabs at Tufte were spot-on and amused me to no end.) It’s a book full of wit and great ideas, but also full of drawn-out sections that require serious focus, and it takes a while to digest it all and put it together in your mind.
So, although I’d highly recommend this book to anyone deeply interested in visualization, I’m still digesting it. What follows is not a review but just notes-to-self from my first read-through: things to follow up on and for my own reference. It might not be particularly thrilling for other readers. Continue reading