notes.txt

 √ do the Update/Enter thing
 √ apply to numeric, categorical, and boolean charts
 √ cumulative sort
 - transition

For transitions, you need a key function eg
  data(d => d.subject, d => d.name)

what indexing function can we use which shows sorting without using the y value as the key?  Do we need access to the rank list?

Nice to display the min & max values overlaid onto bottom & top of at least numeric chart when it's the sort column.  Then think about, if categories are few enough, labeling them when sorted...