d3-array#tickStep JavaScript Examples

export default function tickFormat(start, stop, count, specifier) {
  var step = tickStep(start, stop, count),
      precision;
  specifier = formatSpecifier(specifier == null ? ",f" : specifier);
  switch (specifier.type) {
    case "s": {
      var value = Math.max(Math.abs(start), Math.abs(stop));
      if (specifier.precision == null && !isNaN(precision = precisionPrefix(step, value))) specifier.precision = precision;
      return formatPrefix(specifier, value);
    }
    case "":
    case "e":
    case "g":
    case "p":
    case "r": {
      if (specifier.precision == null && !isNaN(precision = precisionRound(step, Math.max(Math.abs(start), Math.abs(stop))))) specifier.precision = precision - (specifier.type === "e");
      break;
    }
    case "f":
    case "%": {
      if (specifier.precision == null && !isNaN(precision = precisionFixed(step))) specifier.precision = precision - (specifier.type === "%") * 2;
      break;
    }
  }
  return format(specifier);
}

export default function(start, stop, count, specifier) {
  var step = tickStep(start, stop, count),
      precision;
  specifier = formatSpecifier(specifier == null ? ",f" : specifier);
  switch (specifier.type) {
    case "s": {
      var value = Math.max(Math.abs(start), Math.abs(stop));
      if (specifier.precision == null && !isNaN(precision = precisionPrefix(step, value))) specifier.precision = precision;
      return formatPrefix(specifier, value);
    }
    case "":
    case "e":
    case "g":
    case "p":
    case "r": {
      if (specifier.precision == null && !isNaN(precision = precisionRound(step, Math.max(Math.abs(start), Math.abs(stop))))) specifier.precision = precision - (specifier.type === "e");
      break;
    }
    case "f":
    case "%": {
      if (specifier.precision == null && !isNaN(precision = precisionFixed(step))) specifier.precision = precision - (specifier.type === "%") * 2;
      break;
    }
  }
  return format(specifier);
}

export default function(domain, count, specifier) {
  var start = domain[0],
      stop = domain[domain.length - 1],
      step = tickStep(start, stop, count == null ? 10 : count),
      precision;
  specifier = formatSpecifier(specifier == null ? ",f" : specifier);
  switch (specifier.type) {
    case "s": {
      var value = Math.max(Math.abs(start), Math.abs(stop));
      if (specifier.precision == null && !isNaN(precision = precisionPrefix(step, value))) specifier.precision = precision;
      return formatPrefix(specifier, value);
    }
    case "":
    case "e":
    case "g":
    case "p":
    case "r": {
      if (specifier.precision == null && !isNaN(precision = precisionRound(step, Math.max(Math.abs(start), Math.abs(stop))))) specifier.precision = precision - (specifier.type === "e");
      break;
    }
    case "f":
    case "%": {
      if (specifier.precision == null && !isNaN(precision = precisionFixed(step))) specifier.precision = precision - (specifier.type === "%") * 2;
      break;
    }
  }
  return format(specifier);
}

function ticker(year, month, week, day, hour, minute) {

  const tickIntervals = [
    [second,  1,      durationSecond],
    [second,  5,  5 * durationSecond],
    [second, 15, 15 * durationSecond],
    [second, 30, 30 * durationSecond],
    [minute,  1,      durationMinute],
    [minute,  5,  5 * durationMinute],
    [minute, 15, 15 * durationMinute],
    [minute, 30, 30 * durationMinute],
    [  hour,  1,      durationHour  ],
    [  hour,  3,  3 * durationHour  ],
    [  hour,  6,  6 * durationHour  ],
    [  hour, 12, 12 * durationHour  ],
    [   day,  1,      durationDay   ],
    [   day,  2,  2 * durationDay   ],
    [  week,  1,      durationWeek  ],
    [ month,  1,      durationMonth ],
    [ month,  3,  3 * durationMonth ],
    [  year,  1,      durationYear  ]
  ];

  function ticks(start, stop, count) {
    const reverse = stop < start;
    if (reverse) [start, stop] = [stop, start];
    const interval = count && typeof count.range === "function" ? count : tickInterval(start, stop, count);
    const ticks = interval ? interval.range(start, +stop + 1) : []; // inclusive stop
    return reverse ? ticks.reverse() : ticks;
  }

  function tickInterval(start, stop, count) {
    const target = Math.abs(stop - start) / count;
    const i = bisector(([,, step]) => step).right(tickIntervals, target);
    if (i === tickIntervals.length) return year.every(tickStep(start / durationYear, stop / durationYear, count));
    if (i === 0) return millisecond.every(Math.max(tickStep(start, stop, count), 1));
    const [t, step] = tickIntervals[target / tickIntervals[i - 1][2] < tickIntervals[i][2] / target ? i - 1 : i];
    return t.every(step);
  }

  return [ticks, tickInterval];
}

export default function() {
  var dx = 1,
      dy = 1,
      threshold = thresholdSturges,
      smooth = smoothLinear;

  function contours(values) {
    var tz = threshold(values);

    // Convert number of thresholds into uniform thresholds.
    if (!Array.isArray(tz)) {
      const e = extent(values), ts = tickStep(e[0], e[1], tz);
      tz = ticks(Math.floor(e[0] / ts) * ts, Math.floor(e[1] / ts - 1) * ts, tz);
    } else {
      tz = tz.slice().sort(ascending);
    }

    return tz.map(value => contour(values, value));
  }

  // Accumulate, smooth contour rings, assign holes to exterior rings.
  // Based on https://github.com/mbostock/shapefile/blob/v0.6.2/shp/polygon.js
  function contour(values, value) {
    var polygons = [],
        holes = [];

    isorings(values, value, function(ring) {
      smooth(ring, values, value);
      if (area(ring) > 0) polygons.push([ring]);
      else holes.push(ring);
    });

    holes.forEach(function(hole) {
      for (var i = 0, n = polygons.length, polygon; i < n; ++i) {
        if (contains((polygon = polygons[i])[0], hole) !== -1) {
          polygon.push(hole);
          return;
        }
      }
    });

    return {
      type: "MultiPolygon",
      value: value,
      coordinates: polygons
    };
  }

  // Marching squares with isolines stitched into rings.
  // Based on https://github.com/topojson/topojson-client/blob/v3.0.0/src/stitch.js
  function isorings(values, value, callback) {
    var fragmentByStart = new Array,
        fragmentByEnd = new Array,
        x, y, t0, t1, t2, t3;

    // Special case for the first row (y = -1, t2 = t3 = 0).
    x = y = -1;
    t1 = values[0] >= value;
    cases[t1 << 1].forEach(stitch);
    while (++x < dx - 1) {
      t0 = t1, t1 = values[x + 1] >= value;
      cases[t0 | t1 << 1].forEach(stitch);
    }
    cases[t1 << 0].forEach(stitch);

    // General case for the intermediate rows.
    while (++y < dy - 1) {
      x = -1;
      t1 = values[y * dx + dx] >= value;
      t2 = values[y * dx] >= value;
      cases[t1 << 1 | t2 << 2].forEach(stitch);
      while (++x < dx - 1) {
        t0 = t1, t1 = values[y * dx + dx + x + 1] >= value;
        t3 = t2, t2 = values[y * dx + x + 1] >= value;
        cases[t0 | t1 << 1 | t2 << 2 | t3 << 3].forEach(stitch);
      }
      cases[t1 | t2 << 3].forEach(stitch);
    }

    // Special case for the last row (y = dy - 1, t0 = t1 = 0).
    x = -1;
    t2 = values[y * dx] >= value;
    cases[t2 << 2].forEach(stitch);
    while (++x < dx - 1) {
      t3 = t2, t2 = values[y * dx + x + 1] >= value;
      cases[t2 << 2 | t3 << 3].forEach(stitch);
    }
    cases[t2 << 3].forEach(stitch);

    function stitch(line) {
      var start = [line[0][0] + x, line[0][1] + y],
          end = [line[1][0] + x, line[1][1] + y],
          startIndex = index(start),
          endIndex = index(end),
          f, g;
      if (f = fragmentByEnd[startIndex]) {
        if (g = fragmentByStart[endIndex]) {
          delete fragmentByEnd[f.end];
          delete fragmentByStart[g.start];
          if (f === g) {
            f.ring.push(end);
            callback(f.ring);
          } else {
            fragmentByStart[f.start] = fragmentByEnd[g.end] = {start: f.start, end: g.end, ring: f.ring.concat(g.ring)};
          }
        } else {
          delete fragmentByEnd[f.end];
          f.ring.push(end);
          fragmentByEnd[f.end = endIndex] = f;
        }
      } else if (f = fragmentByStart[endIndex]) {
        if (g = fragmentByEnd[startIndex]) {
          delete fragmentByStart[f.start];
          delete fragmentByEnd[g.end];
          if (f === g) {
            f.ring.push(end);
            callback(f.ring);
          } else {
            fragmentByStart[g.start] = fragmentByEnd[f.end] = {start: g.start, end: f.end, ring: g.ring.concat(f.ring)};
          }
        } else {
          delete fragmentByStart[f.start];
          f.ring.unshift(start);
          fragmentByStart[f.start = startIndex] = f;
        }
      } else {
        fragmentByStart[startIndex] = fragmentByEnd[endIndex] = {start: startIndex, end: endIndex, ring: [start, end]};
      }
    }
  }

  function index(point) {
    return point[0] * 2 + point[1] * (dx + 1) * 4;
  }

  function smoothLinear(ring, values, value) {
    ring.forEach(function(point) {
      var x = point[0],
          y = point[1],
          xt = x | 0,
          yt = y | 0,
          v0,
          v1 = values[yt * dx + xt];
      if (x > 0 && x < dx && xt === x) {
        v0 = values[yt * dx + xt - 1];
        point[0] = x + (value - v0) / (v1 - v0) - 0.5;
      }
      if (y > 0 && y < dy && yt === y) {
        v0 = values[(yt - 1) * dx + xt];
        point[1] = y + (value - v0) / (v1 - v0) - 0.5;
      }
    });
  }

  contours.contour = contour;

  contours.size = function(_) {
    if (!arguments.length) return [dx, dy];
    var _0 = Math.floor(_[0]), _1 = Math.floor(_[1]);
    if (!(_0 >= 0 && _1 >= 0)) throw new Error("invalid size");
    return dx = _0, dy = _1, contours;
  };

  contours.thresholds = function(_) {
    return arguments.length ? (threshold = typeof _ === "function" ? _ : Array.isArray(_) ? constant(slice.call(_)) : constant(_), contours) : threshold;
  };

  contours.smooth = function(_) {
    return arguments.length ? (smooth = _ ? smoothLinear : noop, contours) : smooth === smoothLinear;
  };

  return contours;
}

export default function() {
  var x = defaultX,
      y = defaultY,
      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(20);

  function density(data) {
    var values0 = new Float32Array(n * m),
        values1 = new Float32Array(n * m),
        pow2k = Math.pow(2, -k);

    data.forEach(function(d, i, data) {
      var xi = (x(d, i, data) + o) * pow2k,
          yi = (y(d, i, data) + o) * pow2k,
          wi = +weight(d, i, data);
      if (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;
        values0[x0 + y0 * n] += (1 - xt) * (1 - yt) * wi;
        values0[x0 + 1 + y0 * n] += xt * (1 - yt) * wi;
        values0[x0 + 1 + (y0 + 1) * n] += xt * yt * wi;
        values0[x0 + (y0 + 1) * n] += (1 - xt) * yt * wi;
      }
    });

    // TODO Optimize.
    blurX({width: n, height: m, data: values0}, {width: n, height: m, data: values1}, r >> k);
    blurY({width: n, height: m, data: values1}, {width: n, height: m, data: values0}, r >> k);
    blurX({width: n, height: m, data: values0}, {width: n, height: m, data: values1}, r >> k);
    blurY({width: n, height: m, data: values1}, {width: n, height: m, data: values0}, r >> k);
    blurX({width: n, height: m, data: values0}, {width: n, height: m, data: values1}, r >> k);
    blurY({width: n, height: m, data: values1}, {width: n, height: m, data: values0}, r >> k);

    var tz = threshold(values0);

    // Convert number of thresholds into uniform thresholds.
    if (!Array.isArray(tz)) {
      var stop = max(values0);
      tz = tickStep(0, stop, tz);
      tz = range(0, Math.floor(stop / tz) * tz, tz);
      tz.shift();
    }

    return contours()
        .thresholds(tz)
        .size([n, m])
      (values0)
        .map(transform);
  }

  function transform(geometry) {
    geometry.value *= Math.pow(2, -2 * k); // Density in points per square pixel.
    geometry.coordinates.forEach(transformPolygon);
    return geometry;
  }

  function transformPolygon(coordinates) {
    coordinates.forEach(transformRing);
  }

  function transformRing(coordinates) {
    coordinates.forEach(transformPoint);
  }

  // TODO Optimize.
  function transformPoint(coordinates) {
    coordinates[0] = coordinates[0] * Math.pow(2, k) - o;
    coordinates[1] = coordinates[1] * Math.pow(2, k) - o;
  }

  function resize() {
    o = r * 3;
    n = (dx + o * 2) >> k;
    m = (dy + o * 2) >> k;
    return density;
  }

  density.x = function(_) {
    return arguments.length ? (x = typeof _ === "function" ? _ : constant(+_), density) : x;
  };

  density.y = function(_) {
    return arguments.length ? (y = typeof _ === "function" ? _ : constant(+_), density) : y;
  };

  density.weight = function(_) {
    return arguments.length ? (weight = typeof _ === "function" ? _ : constant(+_), density) : weight;
  };

  density.size = function(_) {
    if (!arguments.length) return [dx, dy];
    var _0 = +_[0], _1 = +_[1];
    if (!(_0 >= 0 && _1 >= 0)) throw new Error("invalid size");
    return dx = _0, dy = _1, resize();
  };

  density.cellSize = function(_) {
    if (!arguments.length) return 1 << k;
    if (!((_ = +_) >= 1)) throw new Error("invalid cell size");
    return k = Math.floor(Math.log(_) / Math.LN2), resize();
  };

  density.thresholds = function(_) {
    return arguments.length ? (threshold = typeof _ === "function" ? _ : Array.isArray(_) ? constant(slice.call(_)) : constant(_), density) : threshold;
  };

  density.bandwidth = function(_) {
    if (!arguments.length) return Math.sqrt(r * (r + 1));
    if (!((_ = +_) >= 0)) throw new Error("invalid bandwidth");
    return r = Math.round((Math.sqrt(4 * _ * _ + 1) - 1) / 2), resize();
  };

  return density;
}

export default function() {
  var dx = 1,
      dy = 1,
      threshold = thresholdSturges,
      smooth = smoothLinear;

  function contours(values) {
    var tz = threshold(values);

    // Convert number of thresholds into uniform thresholds.
    if (!Array.isArray(tz)) {
      var domain = extent(values), start = domain[0], stop = domain[1];
      tz = tickStep(start, stop, tz);
      tz = range(Math.floor(start / tz) * tz, Math.floor(stop / tz) * tz, tz);
    } else {
      tz = tz.slice().sort(ascending);
    }

    return tz.map(function(value) {
      return contour(values, value);
    });
  }

  // Accumulate, smooth contour rings, assign holes to exterior rings.
  // Based on https://github.com/mbostock/shapefile/blob/v0.6.2/shp/polygon.js
  function contour(values, value) {
    var polygons = [],
        holes = [];

    isorings(values, value, function(ring) {
      smooth(ring, values, value);
      if (area(ring) > 0) polygons.push([ring]);
      else holes.push(ring);
    });

    holes.forEach(function(hole) {
      for (var i = 0, n = polygons.length, polygon; i < n; ++i) {
        if (contains((polygon = polygons[i])[0], hole) !== -1) {
          polygon.push(hole);
          return;
        }
      }
    });

    return {
      type: "MultiPolygon",
      value: value,
      coordinates: polygons
    };
  }

  // Marching squares with isolines stitched into rings.
  // Based on https://github.com/topojson/topojson-client/blob/v3.0.0/src/stitch.js
  function isorings(values, value, callback) {
    var fragmentByStart = new Array,
        fragmentByEnd = new Array,
        x, y, t0, t1, t2, t3;

    // Special case for the first row (y = -1, t2 = t3 = 0).
    x = y = -1;
    t1 = values[0] >= value;
    cases[t1 << 1].forEach(stitch);
    while (++x < dx - 1) {
      t0 = t1, t1 = values[x + 1] >= value;
      cases[t0 | t1 << 1].forEach(stitch);
    }
    cases[t1 << 0].forEach(stitch);

    // General case for the intermediate rows.
    while (++y < dy - 1) {
      x = -1;
      t1 = values[y * dx + dx] >= value;
      t2 = values[y * dx] >= value;
      cases[t1 << 1 | t2 << 2].forEach(stitch);
      while (++x < dx - 1) {
        t0 = t1, t1 = values[y * dx + dx + x + 1] >= value;
        t3 = t2, t2 = values[y * dx + x + 1] >= value;
        cases[t0 | t1 << 1 | t2 << 2 | t3 << 3].forEach(stitch);
      }
      cases[t1 | t2 << 3].forEach(stitch);
    }

    // Special case for the last row (y = dy - 1, t0 = t1 = 0).
    x = -1;
    t2 = values[y * dx] >= value;
    cases[t2 << 2].forEach(stitch);
    while (++x < dx - 1) {
      t3 = t2, t2 = values[y * dx + x + 1] >= value;
      cases[t2 << 2 | t3 << 3].forEach(stitch);
    }
    cases[t2 << 3].forEach(stitch);

    function stitch(line) {
      var start = [line[0][0] + x, line[0][1] + y],
          end = [line[1][0] + x, line[1][1] + y],
          startIndex = index(start),
          endIndex = index(end),
          f, g;
      if (f = fragmentByEnd[startIndex]) {
        if (g = fragmentByStart[endIndex]) {
          delete fragmentByEnd[f.end];
          delete fragmentByStart[g.start];
          if (f === g) {
            f.ring.push(end);
            callback(f.ring);
          } else {
            fragmentByStart[f.start] = fragmentByEnd[g.end] = {start: f.start, end: g.end, ring: f.ring.concat(g.ring)};
          }
        } else {
          delete fragmentByEnd[f.end];
          f.ring.push(end);
          fragmentByEnd[f.end = endIndex] = f;
        }
      } else if (f = fragmentByStart[endIndex]) {
        if (g = fragmentByEnd[startIndex]) {
          delete fragmentByStart[f.start];
          delete fragmentByEnd[g.end];
          if (f === g) {
            f.ring.push(end);
            callback(f.ring);
          } else {
            fragmentByStart[g.start] = fragmentByEnd[f.end] = {start: g.start, end: f.end, ring: g.ring.concat(f.ring)};
          }
        } else {
          delete fragmentByStart[f.start];
          f.ring.unshift(start);
          fragmentByStart[f.start = startIndex] = f;
        }
      } else {
        fragmentByStart[startIndex] = fragmentByEnd[endIndex] = {start: startIndex, end: endIndex, ring: [start, end]};
      }
    }
  }

  function index(point) {
    return point[0] * 2 + point[1] * (dx + 1) * 4;
  }

  function smoothLinear(ring, values, value) {
    ring.forEach(function(point) {
      var x = point[0],
          y = point[1],
          xt = x | 0,
          yt = y | 0,
          v0,
          v1 = values[yt * dx + xt];
      if (x > 0 && x < dx && xt === x) {
        v0 = values[yt * dx + xt - 1];
        point[0] = x + (value - v0) / (v1 - v0) - 0.5;
      }
      if (y > 0 && y < dy && yt === y) {
        v0 = values[(yt - 1) * dx + xt];
        point[1] = y + (value - v0) / (v1 - v0) - 0.5;
      }
    });
  }

  contours.contour = contour;

  contours.size = function(_) {
    if (!arguments.length) return [dx, dy];
    var _0 = Math.ceil(_[0]), _1 = Math.ceil(_[1]);
    if (!(_0 > 0) || !(_1 > 0)) throw new Error("invalid size");
    return dx = _0, dy = _1, contours;
  };

  contours.thresholds = function(_) {
    return arguments.length ? (threshold = typeof _ === "function" ? _ : Array.isArray(_) ? constant(slice.call(_)) : constant(_), contours) : threshold;
  };

  contours.smooth = function(_) {
    return arguments.length ? (smooth = _ ? smoothLinear : noop, contours) : smooth === smoothLinear;
  };

  return contours;
}

export default function() {
  var x = defaultX,
      y = defaultY,
      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(20);

  function density(data) {
    var values0 = new Float32Array(n * m),
        values1 = new Float32Array(n * m);

    data.forEach(function(d, i, data) {
      var xi = (+x(d, i, data) + o) >> k,
          yi = (+y(d, i, data) + o) >> k,
          wi = +weight(d, i, data);
      if (xi >= 0 && xi < n && yi >= 0 && yi < m) {
        values0[xi + yi * n] += wi;
      }
    });

    // TODO Optimize.
    blurX({width: n, height: m, data: values0}, {width: n, height: m, data: values1}, r >> k);
    blurY({width: n, height: m, data: values1}, {width: n, height: m, data: values0}, r >> k);
    blurX({width: n, height: m, data: values0}, {width: n, height: m, data: values1}, r >> k);
    blurY({width: n, height: m, data: values1}, {width: n, height: m, data: values0}, r >> k);
    blurX({width: n, height: m, data: values0}, {width: n, height: m, data: values1}, r >> k);
    blurY({width: n, height: m, data: values1}, {width: n, height: m, data: values0}, r >> k);

    var tz = threshold(values0);

    // Convert number of thresholds into uniform thresholds.
    if (!Array.isArray(tz)) {
      var stop = max(values0);
      tz = tickStep(0, stop, tz);
      tz = range(0, Math.floor(stop / tz) * tz, tz);
      tz.shift();
    }

    return contours()
        .thresholds(tz)
        .size([n, m])
      (values0)
        .map(transform);
  }

  function transform(geometry) {
    geometry.value *= Math.pow(2, -2 * k); // Density in points per square pixel.
    geometry.coordinates.forEach(transformPolygon);
    return geometry;
  }

  function transformPolygon(coordinates) {
    coordinates.forEach(transformRing);
  }

  function transformRing(coordinates) {
    coordinates.forEach(transformPoint);
  }

  // TODO Optimize.
  function transformPoint(coordinates) {
    coordinates[0] = coordinates[0] * Math.pow(2, k) - o;
    coordinates[1] = coordinates[1] * Math.pow(2, k) - o;
  }

  function resize() {
    o = r * 3;
    n = (dx + o * 2) >> k;
    m = (dy + o * 2) >> k;
    return density;
  }

  density.x = function(_) {
    return arguments.length ? (x = typeof _ === "function" ? _ : constant(+_), density) : x;
  };

  density.y = function(_) {
    return arguments.length ? (y = typeof _ === "function" ? _ : constant(+_), density) : y;
  };

  density.weight = function(_) {
    return arguments.length ? (weight = typeof _ === "function" ? _ : constant(+_), density) : weight;
  };

  density.size = function(_) {
    if (!arguments.length) return [dx, dy];
    var _0 = Math.ceil(_[0]), _1 = Math.ceil(_[1]);
    if (!(_0 >= 0) && !(_0 >= 0)) throw new Error("invalid size");
    return dx = _0, dy = _1, resize();
  };

  density.cellSize = function(_) {
    if (!arguments.length) return 1 << k;
    if (!((_ = +_) >= 1)) throw new Error("invalid cell size");
    return k = Math.floor(Math.log(_) / Math.LN2), resize();
  };

  density.thresholds = function(_) {
    return arguments.length ? (threshold = typeof _ === "function" ? _ : Array.isArray(_) ? constant(slice.call(_)) : constant(_), density) : threshold;
  };

  density.bandwidth = function(_) {
    if (!arguments.length) return Math.sqrt(r * (r + 1));
    if (!((_ = +_) >= 0)) throw new Error("invalid bandwidth");
    return r = Math.round((Math.sqrt(4 * _ * _ + 1) - 1) / 2), resize();
  };

  return density;
}

export function calendar(year, month, week, day, hour, minute, second, millisecond, format) {
  var scale = continuous(identity, identity),
      invert = scale.invert,
      domain = scale.domain;

  var formatMillisecond = format(".%L"),
      formatSecond = format(":%S"),
      formatMinute = format("%I:%M"),
      formatHour = format("%I %p"),
      formatDay = format("%a %d"),
      formatWeek = format("%b %d"),
      formatMonth = format("%B"),
      formatYear = format("%Y");

  var tickIntervals = [
    [second,  1,      durationSecond],
    [second,  5,  5 * durationSecond],
    [second, 15, 15 * durationSecond],
    [second, 30, 30 * durationSecond],
    [minute,  1,      durationMinute],
    [minute,  5,  5 * durationMinute],
    [minute, 15, 15 * durationMinute],
    [minute, 30, 30 * durationMinute],
    [  hour,  1,      durationHour  ],
    [  hour,  3,  3 * durationHour  ],
    [  hour,  6,  6 * durationHour  ],
    [  hour, 12, 12 * durationHour  ],
    [   day,  1,      durationDay   ],
    [   day,  2,  2 * durationDay   ],
    [  week,  1,      durationWeek  ],
    [ month,  1,      durationMonth ],
    [ month,  3,  3 * durationMonth ],
    [  year,  1,      durationYear  ]
  ];

  function tickFormat(date) {
    return (second(date) < date ? formatMillisecond
        : minute(date) < date ? formatSecond
        : hour(date) < date ? formatMinute
        : day(date) < date ? formatHour
        : month(date) < date ? (week(date) < date ? formatDay : formatWeek)
        : year(date) < date ? formatMonth
        : formatYear)(date);
  }

  function tickInterval(interval, start, stop, step) {
    if (interval == null) interval = 10;

    // If a desired tick count is specified, pick a reasonable tick interval
    // based on the extent of the domain and a rough estimate of tick size.
    // Otherwise, assume interval is already a time interval and use it.
    if (typeof interval === "number") {
      var target = Math.abs(stop - start) / interval,
          i = bisector(function(i) { return i[2]; }).right(tickIntervals, target);
      if (i === tickIntervals.length) {
        step = tickStep(start / durationYear, stop / durationYear, interval);
        interval = year;
      } else if (i) {
        i = tickIntervals[target / tickIntervals[i - 1][2] < tickIntervals[i][2] / target ? i - 1 : i];
        step = i[1];
        interval = i[0];
      } else {
        step = Math.max(tickStep(start, stop, interval), 1);
        interval = millisecond;
      }
    }

    return step == null ? interval : interval.every(step);
  }

  scale.invert = function(y) {
    return new Date(invert(y));
  };

  scale.domain = function(_) {
    return arguments.length ? domain(map.call(_, number)) : domain().map(date);
  };

  scale.ticks = function(interval, step) {
    var d = domain(),
        t0 = d[0],
        t1 = d[d.length - 1],
        r = t1 < t0,
        t;
    if (r) t = t0, t0 = t1, t1 = t;
    t = tickInterval(interval, t0, t1, step);
    t = t ? t.range(t0, t1 + 1) : []; // inclusive stop
    return r ? t.reverse() : t;
  };

  scale.tickFormat = function(count, specifier) {
    return specifier == null ? tickFormat : format(specifier);
  };

  scale.nice = function(interval, step) {
    var d = domain();
    return (interval = tickInterval(interval, d[0], d[d.length - 1], step))
        ? domain(nice(d, interval))
        : scale;
  };

  scale.copy = function() {
    return copy(scale, calendar(year, month, week, day, hour, minute, second, millisecond, format));
  };

  return scale;
}

export function calendar(year, month, week, day, hour, minute, second, millisecond, format) {
  var scale = continuous(deinterpolate, reinterpolate),
      invert = scale.invert,
      domain = scale.domain;

  var formatMillisecond = format(".%L"),
      formatSecond = format(":%S"),
      formatMinute = format("%I:%M"),
      formatHour = format("%I %p"),
      formatDay = format("%a %d"),
      formatWeek = format("%b %d"),
      formatMonth = format("%B"),
      formatYear = format("%Y");

  var tickIntervals = [
    [second,  1,      durationSecond],
    [second,  5,  5 * durationSecond],
    [second, 15, 15 * durationSecond],
    [second, 30, 30 * durationSecond],
    [minute,  1,      durationMinute],
    [minute,  5,  5 * durationMinute],
    [minute, 15, 15 * durationMinute],
    [minute, 30, 30 * durationMinute],
    [  hour,  1,      durationHour  ],
    [  hour,  3,  3 * durationHour  ],
    [  hour,  6,  6 * durationHour  ],
    [  hour, 12, 12 * durationHour  ],
    [   day,  1,      durationDay   ],
    [   day,  2,  2 * durationDay   ],
    [  week,  1,      durationWeek  ],
    [ month,  1,      durationMonth ],
    [ month,  3,  3 * durationMonth ],
    [  year,  1,      durationYear  ]
  ];

  function tickFormat(date) {
    return (second(date) < date ? formatMillisecond
        : minute(date) < date ? formatSecond
        : hour(date) < date ? formatMinute
        : day(date) < date ? formatHour
        : month(date) < date ? (week(date) < date ? formatDay : formatWeek)
        : year(date) < date ? formatMonth
        : formatYear)(date);
  }

  function tickInterval(interval, start, stop, step) {
    if (interval == null) interval = 10;

    // If a desired tick count is specified, pick a reasonable tick interval
    // based on the extent of the domain and a rough estimate of tick size.
    // Otherwise, assume interval is already a time interval and use it.
    if (typeof interval === "number") {
      var target = Math.abs(stop - start) / interval,
          i = bisector(function(i) { return i[2]; }).right(tickIntervals, target);
      if (i === tickIntervals.length) {
        step = tickStep(start / durationYear, stop / durationYear, interval);
        interval = year;
      } else if (i) {
        i = tickIntervals[target / tickIntervals[i - 1][2] < tickIntervals[i][2] / target ? i - 1 : i];
        step = i[1];
        interval = i[0];
      } else {
        step = Math.max(tickStep(start, stop, interval), 1);
        interval = millisecond;
      }
    }

    return step == null ? interval : interval.every(step);
  }

  scale.invert = function(y) {
    return new Date(invert(y));
  };

  scale.domain = function(_) {
    return arguments.length ? domain(map.call(_, number)) : domain().map(date);
  };

  scale.ticks = function(interval, step) {
    var d = domain(),
        t0 = d[0],
        t1 = d[d.length - 1],
        r = t1 < t0,
        t;
    if (r) t = t0, t0 = t1, t1 = t;
    t = tickInterval(interval, t0, t1, step);
    t = t ? t.range(t0, t1 + 1) : []; // inclusive stop
    return r ? t.reverse() : t;
  };

  scale.tickFormat = function(count, specifier) {
    return specifier == null ? tickFormat : format(specifier);
  };

  scale.nice = function(interval, step) {
    var d = domain();
    return (interval = tickInterval(interval, d[0], d[d.length - 1], step))
        ? domain(nice(d, interval))
        : scale;
  };

  scale.copy = function() {
    return copy(scale, calendar(year, month, week, day, hour, minute, second, millisecond, format));
  };

  return scale;
}