Hog wild about dot maps

Reader Chris P. sent me this chart.

This was meant to be "light entertainment." See the Twitter discussion below.



Let's think a bit about the dot map as a data graphic.

Dot maps are one dimensional. The dot's location is used to indicate the latitude and longitude and therefore the x,y coordinates cannot encode any other data. If we have basically a black/white chart, as in this hog map, the dot can only encode binary data (yes/no).

The legend says "each dot represents 5,000 hogs." Think about how that statement applies to these scenarios:

  • Do you expect to see something different between the dot representing 4,200 and the one showing 4,900?
  • Do you expect to see something different between the dot representing 400 and 4,000?
  • Do you expect to see something different between the location with 4,800 hogs and 9,600 hogs?

Based on the legend, the designer would need two dots to represent 10,000 hogs. But those two dots pertain to the same location. Sometimes, "jitter" is added, and the two dots are placed side by side. However, with the scale of the map of the U.S., and the dots representing seemingly small neighborhoods, jitter creates more confusion than anything. Also, what about 3, 4, 5, .. dots in the same location?


Looking at the details above, are the dots jittered or do they represent neighboring locations?

Sometimes, colors are used to encode data on a dot map. But each dot can only contain one color, so it only typically shows the top category in each location.

Dot maps are very limited. Think before you use them.


Light entertainment: this looks like a bar chart

Long-time reader Daniel L. said this made him laugh.


This prompted me revive a feature I used to run on here called "Light entertainment." Dataviz work that are so easy to ridicule that one wonders if they weren't just made for the laughs. See all previous installments here.

Daniel also said it fails the Trifecta Checkup. What is the question the chart is addressing and what's the message? It's a bar chart, the axis not starting at zero, with multiple colors and Moire effects. and missing labels!