Heatmap coloring (2011)

There's been a lot of movement in the past few years on colormaps informed by studies of human perception.

Viridis, now the matplotlib default, is quite popular:

* https://bids.github.io/colormap/

* https://cran.r-project.org/web/packages/viridis/vignettes/in...

Google recently introduced an improvement on the venerable "jet" colormap called Turbo: https://ai.googleblog.com/2019/08/turbo-improved-rainbow-col...

This is an article about 2d histogram colouring where they discuss how you get a better colouring if you set the saturation of each bin by it's (columnwise) rank: that is you sort all values in each column and assign a saturation of 1 to the bin with the largest count, and then progressively smaller saturations as you go down the rankings.

Presumably they don't care their column wise colouring scheme makes it impossible to sensibly compare across the rows as each column gets its own colour scale. shrug