Function line

explainshell/web/static/js/d3.v3.js:3683–3698

(data)

  function d3_svg_line(projection) {
    var x = d3_svg_lineX, y = d3_svg_lineY, defined = d3_true, interpolate = d3_svg_lineLinear, interpolateKey = interpolate.key, tension = .7;
    function line(data) {
      var segments = [], points = [], i = -1, n = data.length, d, fx = d3_functor(x), fy = d3_functor(y);
      function segment() {
        segments.push("M", interpolate(projection(points), tension));
      }
      while (++i < n) {
        if (defined.call(this, d = data[i], i)) {
          points.push([ +fx.call(this, d, i), +fy.call(this, d, i) ]);
        } else if (points.length) {
          segment();
          points = [];
        }
      }
      if (points.length) segment();
      return segments.length ? segments.join("") : null;
    }
    line.x = function(_) {
      if (!arguments.length) return x;
      x = _;