interpolateBalanced?

[Fil]

interpolateRound(0,2) gives more space to intermediate values (1) than to the ends (0 and 2). interpolateBalanced would give them equal space.

See https://observablehq.com/@fil/interpolatebalanced

[mbostock]

Feels too niche to me.

[jrus]

Can’t you just..

draw(interpolateRound(-0.5, 2.5))

[Fil]

No, there are tiny bugs with that formula (at the ends, in your case -0 (sort-of okay, my formula does this too) and 3 ❌).

but we can adapt it a bit:

interpolateBalanced = (a, b) => {
  // epsilon is needed to have an exact value for t=1
  var sign = Math.sign(b - a);
  return interpolateRound(
    a - sign * (0.5 - epsilon),
    b + sign * (0.5 - epsilon)
  );
}