d3.scale.quantize = function() {

  return d3_scale_quantize(0, 1, [0, 1]);

};

function d3_scale_quantize(x0, x1, range) {

  var kx, i;

  function scale(x) {

    return range[Math.max(0, Math.min(i, Math.floor(kx * (x - x0))))];

  }

  function rescale() {

    kx = range.length / (x1 - x0);

    i = range.length - 1;

    return scale;

  }

  scale.domain = function(x) {

    if (!arguments.length) return [x0, x1];

    x0 = +x[0];

    x1 = +x[x.length - 1];

    return rescale();

  };

  scale.range = function(x) {

    if (!arguments.length) return range;

    range = x;

    return rescale();

  };

  scale.copy = function() {

    return d3_scale_quantize(x0, x1, range); // copy on write

  };

  return rescale();

};