Getting information from a table is like extracting sunlight from a cucumber. (Farquhar & Farquhar, 1891) (fn:3)

With repetition I'll be able to abstract and simplify the code to produce an alternative for histograms(bar-charts). With that in mind, I re-visited some data from Mike Davis's Planet of Slums to make this Percent-Scale-Labeled-Line plot of data.

The countries are ordered by millions of residents in slums, but the lines show what percentage of the urban population is taken up by those millions. The USA has a million more people in slums than Egypt, but twelve point eight million people is smaller percentage of its urban population. Later it might be interestingto compare my too-complex gnuplot code with my getting-simpler Racket code for this data and visualization.

While working with the PercentScale-LineLabel code, some advice came to mind. Visualizations get better with higher ink-to-information ratios so we should avoid labels and any other “presentation bureacracy” when possible. I also felt that it was disorienting to label the percent-scaled lines with the figure for millions of people. With an Howard Wainer article (fn:3) coming to mind, it seemed better to make the visualization simpler, more table-like, but still with the aid to understanding provide by lines showing how the figure for millions relates to a particular country's total urban population. I keep the lines because of a few paragraphs from Solomon Messing's blog post(fn:4): > ... judgements about position relative to a baseline are dramatically more accurate than judgements about angles, area, or length (with no baseline).

I'm hoping the lines and position of the percentage figures will be helpful since they all share the same baseline. And I thing the figures in millions needs some sort of context for each country.

I suppose the plot above could help with the book's table. With more time I'd like to work in a line that shows the percentage of the entire world's slum population in each country. Or maybe a line that shows each country's population in proportion to the country with the greatest population. But I suppose it's easy enough to answer certain questions with this simple visualization. It's not too hard to mentally calculate that Ethiopia and Tanzania, while having a high proportion of their urban populations in slums, have less slum populations that are less than ten percent as large as China's.