Function polymap

docs/tests/v2/es6/js/sanddance.js:107066–107086

(domain, range, interpolate)

}

function polymap(domain, range, interpolate) {
  var j = Math.min(domain.length, range.length) - 1,
      d = new Array(j),
      r = new Array(j),
      i = -1; // Reverse descending domains.

  if (domain[j] < domain[0]) {
    domain = domain.slice().reverse();
    range = range.slice().reverse();
  }

  while (++i < j) {
    d[i] = normalize(domain[i], domain[i + 1]);
    r[i] = interpolate(range[i], range[i + 1]);
  }

  return function (x) {
    var i = (0, _d3Array.bisect)(domain, x, 1, j) - 1;
    return r[i](d[i](x));
  };
}

function copy(source, target) {
  return target.domain(source.domain()).range(source.range()).interpolate(source.interpolate()).clamp(source.clamp()).unknown(source.unknown());