I understand that the true Sankey diagram specifically accounts for movement of a constant amount of something through a system or process; but I find myself wanting to make the same sort of graceful arrow diagram with non-atomic items, like database records or something. Specifically, say I have 10,000 items, and at a certain step they get merged into 4,000 items. The "other 6,000" shouldn't go in an arrow off to the side; they didn't get eliminated. 10K simply became 4K without actual loss.
The Minard Napoleon plot includes loss by invisible attrition, which could give essentially the same effect; but in general it's gradual loss over more or less continuous time. I'm looking for something that will show the diminution of merging (i.e. the 10K to 4K) at a discrete step of the process, with the big friendly rounded block arrows that are common in Sankey-drawing software. I would specifically want rounded "shoulders" on the transition point, not two adjoining rectangles. Does anybody know of a package that will do that? Thanks!
