interpolateBasis function Value interpolation

num Function(num) interpolateBasis(List<num> values)

Returns a uniform nonrational B-spline interpolator through the specified list of values, which must be numbers.

Implicit control points are generated such that the interpolator returns values[0] at t = 0 and values[values.length - 1] at t = 1. See also d3.curveBasis.

Implementation

num Function(num) interpolateBasis(List<num> values) {
  var n = values.length - 1;
  return (num t) {
    int i;
    if (t <= 0) {
      t = 0;
      i = 0;
    } else if (t >= 1) {
      t = 1;
      i = n - 1;
    } else {
      // t = t * n;
      i = (t * n).floor();
    }
    var v1 = values[i],
        v2 = values[i + 1],
        v0 = i > 0 ? values[i - 1] : 2 * v1 - v2,
        v3 = i < n - 1 ? values[i + 2] : 2 * v2 - v1;
    return basis((t - i / n) * n, v0, v1, v2, v3);
  };
}