saga wrote: ↑Sat Jan 04, 2025 7:55 amDot distribution maps can communicate these things (if there's no overlap!) either by counting or estimating visual mass.
"Estimating visual mass" works just as well with heat maps (which is not very - I know from experience that my intuition is pretty bad about estimating numbers without actually counting things). And even when the dots don't overlap, there's usually enough of them that I wouldn't care to actually count them. If you want to show exact counts, it's better to just print the numbers.
Sometimes, the best answer is even to not draw a map at all but just list your data in tables!
Still, one way to deal with overlapping dots would be to, like heat maps, show them as a more intense color. The effect would be like a Venn diagram:
- two dots.png (3.21 KiB) Viewed 195062 times
But even that fails if you have too many in one place. With examples where density varies dramatically over different parts of the map, the only viable solution is to use different sizes of dots, and use a key/legend to communicate "a dot of this size means one million people, a dot of this size means ten million people, etc.". (
Maybe you can do this in a way to area is preserved: i.e., make the radius of the circle proportional to the square root of the number of items it represents. Though some things have such varying densities that even that would make it difficult to represent both high-density and low-density areas meaningfully on the same map. In practice, I've found that varying-dot-size maps often use logarithmic dot sizes.) This is also easier to count, since people would much rather count a small number of large dots than a large number of small ones. However, my intuition is still bad at estimating at a glance how many small dots it takes to overpower the large ones.