hmm... I would describe it as something like a '2D histogram square-bin plot' a 'categorical plot' or perhaps a variant of a 'mosaic plot' using color density i

hmm... I would describe it as something like a '2D histogram square-bin plot' a 'categorical plot' or perhaps a variant of a 'mosaic plot' using color density instead of area. http://www.math.yorku.ca/SCS/sugi/sugi17-paper.html http://www.math.yorku.ca/SCS/sugi/sugi17-paper.html http://en.wikipedia.org/wiki/Mosaic_plot http://en.wikipedia.org/wiki/Mosaic_plot