Function density

external/.d3.js:6610–6741

()

}

function density() {
  var x = defaultX$1,
      y = defaultY$1,
      weight = defaultWeight,
      dx = 960,
      dy = 500,
      r = 20, // blur radius
      k = 2, // log2(grid cell size)
      o = r * 3, // grid offset, to pad for blur
      n = (dx + o * 2) >> k, // grid width
      m = (dy + o * 2) >> k, // grid height
      threshold = constant$5(20);

  function grid(data) {
    var values = new Float32Array(n * m),
        pow2k = Math.pow(2, -k),
        i = -1;

    for (const d of data) {
      var xi = (x(d, ++i, data) + o) * pow2k,
          yi = (y(d, i, data) + o) * pow2k,
          wi = +weight(d, i, data);
      if (wi && xi >= 0 && xi < n && yi >= 0 && yi < m) {
        var x0 = Math.floor(xi),
            y0 = Math.floor(yi),
            xt = xi - x0 - 0.5,
            yt = yi - y0 - 0.5;
        values[x0 + y0 * n] += (1 - xt) * (1 - yt) * wi;
        values[x0 + 1 + y0 * n] += xt * (1 - yt) * wi;
        values[x0 + 1 + (y0 + 1) * n] += xt * yt * wi;
        values[x0 + (y0 + 1) * n] += (1 - xt) * yt * wi;
      }
    }

    blur2({data: values, width: n, height: m}, r * pow2k);
    return values;
  }

  function density(data) {
    var values = grid(data),
        tz = threshold(values),
        pow4k = Math.pow(2, 2 * k);

    // Convert number of thresholds into uniform thresholds.
    if (!Array.isArray(tz)) {
      tz = ticks(Number.MIN_VALUE, max$3(values) / pow4k, tz);
    }

    return Contours()
        .size([n, m])
        .thresholds(tz.map(d => d * pow4k))
      (values)
        .map((c, i) => (c.value = +tz[i], transform(c)));
  }

  density.contours = function(data) {
    var values = grid(data),
        contours = Contours().size([n, m]),