I haven't worked through it yet,
but I think the methods described in this post on Kaplan Meier curves
may be of use for you:
Essentially, there will need to be some data padding to get the
Great answer. I was getting to the same result... just not as fast or as neatly as you do. I wish there was a way that I could get a tooltip on each problem. Unfortunately, we can't seem to break the aggregation, so that if we add "Problem" on the tooltip, the vertical lines have "Problem: *" in the tooltip.