如何在D3.js v4/v5中实现适配区域图的自定义bundle插值曲线

请参考以下使用basis插值的D3.js图表：

在D3.js v3版本中，我可以通过bundle插值（.interpolate("bundle").tension(0)）为区域图实现如下渲染效果：

可以看到图表各段与邻段完美衔接，这正是我需要的效果。

在D3.js v4与v5版本中，bundle插值的语法变为.curve(d3.curveBundle)，但该方法现在仅适用于d3.line，不适用于d3.area。

我近期从v3升级至v5，因此尝试创建可适配区域图的自定义bundle曲线，以保留v3时期的插值效果。

我已接近目标，以下是目前编写的代码：

///////////////////// Custom curves.
/** Bundle-ish.
 * Trying to adapt curveBundle for use with areas… */
function myBundle(context, beta) {
  this._basis = new d3.curveBasis(context);
  this._beta = beta;
  this._context = context; // temporary. shouldn't be needed for bundle.
}
myBundle.prototype = {
  areaStart: function() {
    this._line = 0;
  },
  areaEnd: function() {
    this._line = NaN;
  },
  lineStart: function() {
    this._x = [];
    this._y = [];
    this._basis.lineStart();
  },
  lineEnd: function() {
    var x = this._x, y = this._y, j = x.length - 1;
    if (j > 0) {
      var x0 = x[0], y0 = y[0], dx = x[j] - x0, dy = y[j] - y0, i = -1, t;
      while (++i <= j) {
        t = i / j;
        this._basis.point(
          this._beta * x[i] + (1 - this._beta) * (x0 + t * dx),
          this._beta * y[i] + (1 - this._beta) * (y0 + t * dy)
        );
      }
    }
    this._x = this._y = null;
    this._basis.lineEnd();
  },
  point: function(x, y) {
    this._x.push(+x);
    this._y.push(+y);
    // console.log( this._x.push(+x), this._y.push(+y) );
  }
};

myCurveBundle = (function custom(beta) {
  function myCurveBundle(context) {
    return beta === 1 ? new myBasis(context) : new myBundle(context, beta);
  }
  myCurveBundle.beta = function(beta) {
    return custom(+beta);
  };
  return myCurveBundle;
})(0.85);

/////////////////// The chart.
var width = 960;
var height = 540;
var data = [];
data.prosody = [116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.473, 116.578, 125.552, 134.888, 144.225, 153.561, 162.898, 172.235, 181.571, 190.908, 200.244, 209.581, 218.917, 227.715, 218.849, 209.591, 200.333, 191.076, 181.818, 172.560, 163.302, 154.044, 144.787, 135.529, 126.271, 117.013, 107.755, 98.498, 89.240, 97.511, 118.857, 140.202, 161.547, 182.893, 192.100, 188.997, 185.895, 182.792, 179.690, 176.587, 173.485, 170.382, 167.280, 164.177, 161.075, 157.972, 154.870, 151.767, 148.665, 145.562, 142.460, 139.357, 136.255, 133.152, 130.050, 126.947, 124.244, 122.275, 120.307, 118.338, 116.369, 114.400, 112.431, 110.462, 108.493, 106.524, 104.555, 102.586, 100.617, 98.648, 99.659, 101.531, 103.402, 105.273, 107.145, 109.016, 110.887, 112.758, 114.630, 116.501, 118.372, 120.244, 122.115, 123.986, 125.857, 127.729, 129.600, 131.471, 133.343, 135.214, 137.085, 138.956, 140.828, 142.699, 144.570, 146.442, 148.313, 150.184, 149.175, 146.384, 143.594, 140.803, 138.013, 135.222, 132.432, 129.642, 126.851, 124.061, 121.270, 118.480, 115.689, 112.899, 110.109, 107.318, 104.528, 101.737, 98.947, 96.156, 93.366, 90.576, 87.785, 84.995, 82.204, 79.414, 76.623, 0, 0, 0, 0, 0, 0, 76.601, 78.414, 80.227, 82.041, 83.854, 85.667, 87.480, 89.294, 91.107, 92.920, 94.733, 96.547, 98.360, 100.173, 101.986, 103.800, 105.613, 107.426, 109.239, 111.053, 112.866, 114.679, 116.492, 115.917, 114.338, 112.760, 111.181, 109.602, 108.023, 106.444, 104.865, 103.286, 101.707, 100.128, 98.549, 96.970, 95.391, 93.812, 92.233, 90.654, 89.075, 87.534, 88.055, 88.646, 89.237, 89.827, 90.418, 91.009, 91.600, 92.191, 92.782, 93.373, 93.964, 94.555, 95.146, 95.737, 96.328, 96.919, 97.509, 98.100, 98.691, 99.282, 99.873, 100.062, 98.230, 96.399, 94.567, 92.736, 90.904, 89.072, 87.241, 85.409, 83.578, 81.746, 79.914, 78.083, 78.839, 80.880, 82.922, 84.964, 87.006, 89.048, 91.090, 93.132, 95.174, 97.216, 99.257, 101.299, 103.341, 105.383, 107.425, 109.467, 111.509, 113.551, 112.633, 110.755, 108.877, 106.999, 105.121, 103.243, 101.365, 99.487, 97.609, 95.731, 93.853, 91.975, 90.097, 88.219, 86.341, 84.463, 82.585, 80.707, 78.829, 76.951, 78.067, 81.290, 84.513, 87.

内容的提问来源于stack exchange，提问作者Fabien Snauwaert