This example shows a bar chart transitioning between two overlapping subsets of data. Rather than moving everything at once, the staging breaks it down into sets of transitions that remove old marks, update live ones, and add new ones.

The staging is done with a technique similar to [this one](https://gist.github.com/miguelmota/3faa2a2954f5249f61d9). A counter is used to keep track of outstanding transitions in a group and then move on the next one when all of the transitions have completed.