Just for reference, this representation of tone reproduction is called a Dorst diagram (proposed by Dorst in the 40s). It was proposed as an alternative to the "windmill"/quadrants representation which is from Jones.

Interestingly, re-reading the short section on this in Henry, apparently the original Jones study included windmill diagrams with up to 10 transitions, which must have been quite complicated to follow. Perhaps this is one of the reasons for Dorst's proposal, which although less "graphical", seems easier to follow when more than a few transitions are involved.