xAxis.js

// Use the axis in the initialize method of your BarChart, like this:

d3.chart('BarChart', {
  
  initialize: function() {
    ...
    chart.xAxis = this.base.select('g').append('g').chart('xAxis', {parent: this});
    this.attach('axis', chart.xAxis);
  }
  
})


/*
  The axis component
*/
d3.chart('xAxis', {

  initialize: function(options) {
    var component = this,
        chart = options.parent;

    this._name = 'xAxis';
    // Must pass in a chart that has a scale and height
    this.xScale = chart.xScale();

    this._customTimeFormat = d3.time.format.multi([
      [".%L", function(d) { return d.getMilliseconds(); }],
      [":%S", function(d) { return d.getSeconds(); }],
      ["%-I:%M", function(d) { return d.getMinutes(); }],
      ["%-I %p", function(d) { return d.getHours(); }],
      ["%a %-d", function(d) { return d.getDay() && d.getDate() != 1; }],
      ["%b %-d", function(d) { return d.getDate() != 1; }],
      ["%B", function(d) { return d.getMonth(); }],
      ["%Y", function() { return true; }]
    ]);

    this._xAxis = d3.svg.axis()
      .scale(this.xScale)
      .orient('bottom')
      // .tickFormat(this._customTimeFormat)
      ;
    this._rotation = 0;

    this.base
      .classed('x axis', true)
      .attr('transform', 'translate(0, ' + chart.height() +')');

    chart.on('change:height', function(newHeight) {
      component.base.attr('transform', 'translate(0, ' + chart.height() +')');
    });

    this.layer('axis', component.base, {

      dataBind : function(data) {
        return this.selectAll('g').data([data]);
      },

      insert : function() {
        return this.append('g').classed('x axis wrapper', true);
      },

      events: {
        'merge:transition': function() {
          var transformString = 'translate(0, 19)';
          if (component.rotation()) {
            transformString += 'rotate('+component.rotation()+')';
          }


          this.duration(chart.duration()).call(component._xAxis)
            .selectAll('text')
            .attr('y', 0)
            .attr('dy', 0)
            .attr('transform', transformString)
            .style('text-anchor', component.rotation() ? 'start' : 'middle')
            ;
        }
      }

    });
  },

 /*
  * chart.rotation(*degrees*)
  *  
  * Sets the rotation of the labels.
  */
  rotation: function(degrees) {
    if (arguments.length === 0) {
      return this._rotation;
    }

    this._rotation = degrees;

    return this;
  },

  /*
   * chart.hide(*boolean*)
   *
   * Determines whether the component is visible
   */
  hide: function(bool) {
    if (arguments.length === 0) {
      return this.base.attr('display') == 'none';
    }

    if (bool) {
      this.base.attr('display', 'none');
    } else {
      this.base.attr('display', 'initial');
    }

    return this;
  },

  /*
   * chart.hideTicks(*bool*)
   * 
   * Determines whether tick marks are shown.
   */
  hideTicks: function(bool) {
    if (arguments.length === 0) {
      return this;
    }

    if (bool) {this._xAxis.tickSize(0);}
    //else {//this.xAxis.tickFormat(');}

    return this;
  },

  /*
   * chart.ticks(*integer*)
   * 
   * Sets the number of ticks.
   */
  ticks: function(_) {
    if (arguments.length === 0) {
      return this._xAxis.ticks();
    }

    this._xAxis.ticks(_);

    return this;
  }

});