Hover labels and event data for cumulative histograms

[alexcjohnson]

In #2113 we're adding bin range information to histogram hover labels, and input point numbers to the event data. But CDFs were explicitly omitted from these changes because it's not so obvious how to handle them.

My comment from that PR:

this gets at some of the same issues that led to cumulative.currentbin but in principle a CDF shows the sum of all the data prior to a specific point, not the data within that bin. perhaps I should shift p0 and p1 depending on currentbin so that the hover label at least gets the description "all the data prior to X" precisely correct, even though it'll be a different value than the center of the bar...

And then what about pts? You could say it should be included and again should be "all the data prior to X" but then it would be meaningless to select a single bar and not all the bars before it. Alternatively pts could contain "all the data that was added in this bar" which might be more useful in terms of selecting a single bar, but it's not really what that bar means.

Response from @etpinard:

so that the hover label at least gets the description "all the data prior to X"

Yeah. I think something along those lines would be useful down the road.

You could say it should be included and again should be "all the data prior to X" but then it would be meaningless to select a single bar and not all the bars before it. Alternatively pts could contain "all the data that was added in this bar"

Sounds to me like both all-data-prior-to-X and data-added-in-this-bar point lists could be useful, so we might have to emit both in the future.

[julioasotodv]

+1 for this. It just seems weird that the hover info for a cumulative histogram is not actually showing the "up to" value, and instead shows the in-the-middle value for the bin range.

[akshata-patel19]

Any updates on this? would like to see the data labels as a list when hovering over a histogram bin