Function d3_svg_lineFiniteDifferences

explainshell/web/static/js/d3.v3.js:3900–3907

(points)

    return (p1[1] - p0[1]) / (p1[0] - p0[0]);
  }
  function d3_svg_lineFiniteDifferences(points) {
    var i = 0, j = points.length - 1, m = [], p0 = points[0], p1 = points[1], d = m[0] = d3_svg_lineSlope(p0, p1);
    while (++i < j) {
      m[i] = (d + (d = d3_svg_lineSlope(p0 = p1, p1 = points[i + 1]))) / 2;
    }
    m[i] = d;
    return m;
  }
  function d3_svg_lineMonotoneTangents(points) {
    var tangents = [], d, a, b, s, m = d3_svg_lineFiniteDifferences(points), i = -1, j = points.length - 1;
    while (++i < j) {