The default tickFormat with a collapsed domain lacks sufficient precision

[Fil]

d3.scaleLinear().domain([5.5, 5.5]).tickFormat(7.5)(5.5) // "6"

We don’t handle the tick step being zero well.

(originally observablehq/plot#2076 (comment))

[IspolatovDenis]

When a zero-size domain is specified, values ​​outside that domain are scaled to the center, which seems counterintuitive.
Example:

• const scale = d3.scaleLinear().domain([10, 10]).range([0, 100])
• scale(10) // expect 50 (?)
• scale(9) // expect some less than 0 or Infinity(or -Infinity?)
• scale(11) // expect some more than 100 (or Infinity?)

[Fil]

Thanks. Did you test #287?