nv.models.axis = function() {

  //============================================================
  // Public Variables with Default Settings
  //------------------------------------------------------------

  var axis = d3.svg.axis()
    ;

  var margin = {top: 0, right: 0, bottom: 0, left: 0}
    , width = 60 //only used for tickLabel currently
    , height = 60 //only used for tickLabel currently
    , scale = d3.scale.linear()
    , axisLabelText = null
    , showMaxMin = true //TODO: showMaxMin should be disabled on all ordinal scaled axes
    , highlightZero = true
    , rotateLabels = 0
    , rotateYLabel = true
    , staggerLabels = false
    , ticks = null
    ;

  axis
    .scale(scale)
    .orient('bottom')
    .tickFormat(function(d) { return d })
    ;

  //============================================================


  //============================================================
  // Private Variables
  //------------------------------------------------------------

  var scale0;

  //============================================================


  function chart(selection) {
    selection.each(function(data) {
      var container = d3.select(this);


      //------------------------------------------------------------
      // Setup containers and skeleton of chart

      var wrap = container.selectAll('g.nv-wrap.nv-axis').data([data]);
      var wrapEnter = wrap.enter().append('g').attr('class', 'nvd3 nv-wrap nv-axis');
      var gEnter = wrapEnter.append('g');
      var g = wrap.select('g')

      //------------------------------------------------------------


      if (ticks !== null)
        axis.ticks(ticks);
      else if (axis.orient() == 'top' || axis.orient() == 'bottom')
        axis.ticks(Math.abs(scale.range()[1] - scale.range()[0]) / 100);


      //TODO: consider calculating width/height based on whether or not label is added, for reference in charts using this component


      d3.transition(g)
          .call(axis);

      scale0 = scale0 || axis.scale();

      var fmt = axis.tickFormat();
      if (fmt == null) {
        fmt = scale0.tickFormat();
      }

      var axisLabel = g.selectAll('text.nv-axislabel')
          .data([axisLabelText || null]);
      axisLabel.exit().remove();
      switch (axis.orient()) {
        case 'top':
          axisLabel.enter().append('text').attr('class', 'nv-axislabel')
              .attr('text-anchor', 'middle')
              .attr('y', 0);
          var w = (scale.range().length==2) ? scale.range()[1] : (scale.range()[scale.range().length-1]+(scale.range()[1]-scale.range()[0]));
          axisLabel
              .attr('x', w/2);
          if (showMaxMin) {
            var axisMaxMin = wrap.selectAll('g.nv-axisMaxMin')
                           .data(scale.domain());
            axisMaxMin.enter().append('g').attr('class', 'nv-axisMaxMin').append('text');
            axisMaxMin.exit().remove();
            axisMaxMin
                .attr('transform', function(d,i) {
                  return 'translate(' + scale(d) + ',0)'
                })
              .select('text')
                .attr('dy', '0em')
                .attr('y', -axis.tickPadding())
                .attr('text-anchor', 'middle')
                .text(function(d,i) {
                  var v = fmt(d);
                  return ('' + v).match('NaN') ? '' : v;
                });
            d3.transition(axisMaxMin)
                .attr('transform', function(d,i) {
                  return 'translate(' + scale.range()[i] + ',0)'
                });
          }
          break;
        case 'bottom':
          var xLabelMargin = 30;
          var maxTextWidth = 30;
          var xTicks = g.selectAll('g').select("text");
          if (rotateLabels%360) {
            //Calculate the longest xTick width
            xTicks.each(function(d,i){
              var width = this.getBBox().width;
              if(width > maxTextWidth) maxTextWidth = width;
            });
            //Convert to radians before calculating sin. Add 30 to margin for healthy padding.
            var sin = Math.abs(Math.sin(rotateLabels*Math.PI/180));
            var xLabelMargin = (sin ? sin*maxTextWidth : maxTextWidth)+30;
            //Rotate all xTicks
            xTicks
              .attr('transform', function(d,i,j) { return 'rotate(' + rotateLabels + ' 0,0)' })
              .attr('text-anchor', rotateLabels%360 > 0 ? 'start' : 'end');
          }
          axisLabel.enter().append('text').attr('class', 'nv-axislabel')
            .attr('text-anchor', 'middle')
            .attr('y', xLabelMargin);
          var w = (scale.range().length==2) ? scale.range()[1] : (scale.range()[scale.range().length-1]+(scale.range()[1]-scale.range()[0]));
          axisLabel
              .attr('x', w/2);
          if (showMaxMin) {
            var axisMaxMin = wrap.selectAll('g.nv-axisMaxMin')
                           .data(scale.domain());
            axisMaxMin.enter().append('g').attr('class', 'nv-axisMaxMin').append('text');
            axisMaxMin.exit().remove();
            axisMaxMin
                .attr('transform', function(d,i) {
                  return 'translate(' + scale(d) + ',0)'
                })
              .select('text')
                .attr('dy', '.71em')
                .attr('y', axis.tickPadding())
                .attr('transform', function(d,i,j) { return 'rotate(' + rotateLabels + ' 0,0)' })
                .attr('text-anchor', rotateLabels ? (rotateLabels%360 > 0 ? 'start' : 'end') : 'middle')
                .text(function(d,i) {
                  var v = fmt(d);
                  return ('' + v).match('NaN') ? '' : v;
                });
            d3.transition(axisMaxMin)
                .attr('transform', function(d,i) {
                  return 'translate(' + scale.range()[i] + ',0)'
                });
          }
          if (staggerLabels)
            xTicks
                .attr('transform', function(d,i) { return 'translate(0,' + (i % 2 == 0 ? '0' : '12') + ')' });

          break;
        case 'right':
          axisLabel.enter().append('text').attr('class', 'nv-axislabel')
              .attr('text-anchor', rotateYLabel ? 'middle' : 'begin')
              .attr('transform', rotateYLabel ? 'rotate(90)' : '')
              .attr('y', rotateYLabel ? (-Math.max(margin.right,width) - 12) : -10); //TODO: consider calculating this based on largest tick width... OR at least expose this on chart
          axisLabel
              .attr('x', rotateYLabel ? (scale.range()[0] / 2) : axis.tickPadding());
          if (showMaxMin) {
            var axisMaxMin = wrap.selectAll('g.nv-axisMaxMin')
                           .data(scale.domain());
            axisMaxMin.enter().append('g').attr('class', 'nv-axisMaxMin').append('text')
                .style('opacity', 0);
            axisMaxMin.exit().remove();
            axisMaxMin
                .attr('transform', function(d,i) {
                  return 'translate(0,' + scale(d) + ')'
                })
              .select('text')
                .attr('dy', '.32em')
                .attr('y', 0)
                .attr('x', axis.tickPadding())
                .attr('text-anchor', 'start')
                .text(function(d,i) {
                  var v = fmt(d);
                  return ('' + v).match('NaN') ? '' : v;
                });
            d3.transition(axisMaxMin)
                .attr('transform', function(d,i) {
                  return 'translate(0,' + scale.range()[i] + ')'
                })
              .select('text')
                .style('opacity', 1);
          }
          break;
        case 'left':
          axisLabel.enter().append('text').attr('class', 'nv-axislabel')
              .attr('text-anchor', rotateYLabel ? 'middle' : 'end')
              .attr('transform', rotateYLabel ? 'rotate(-90)' : '')
              .attr('y', rotateYLabel ? (-Math.max(margin.left,width) + 12) : -10); //TODO: consider calculating this based on largest tick width... OR at least expose this on chart
          axisLabel
              .attr('x', rotateYLabel ? (-scale.range()[0] / 2) : -axis.tickPadding());
          if (showMaxMin) {
            var axisMaxMin = wrap.selectAll('g.nv-axisMaxMin')
                           .data(scale.domain());
            axisMaxMin.enter().append('g').attr('class', 'nv-axisMaxMin').append('text')
                .style('opacity', 0);
            axisMaxMin.exit().remove();
            axisMaxMin
                .attr('transform', function(d,i) {
                  return 'translate(0,' + scale0(d) + ')'
                })
              .select('text')
                .attr('dy', '.32em')
                .attr('y', 0)
                .attr('x', -axis.tickPadding())
                .attr('text-anchor', 'end')
                .text(function(d,i) {
                  var v = fmt(d);
                  return ('' + v).match('NaN') ? '' : v;
                });
            d3.transition(axisMaxMin)
                .attr('transform', function(d,i) {
                  return 'translate(0,' + scale.range()[i] + ')'
                })
              .select('text')
                .style('opacity', 1);
          }
          break;
      }
      axisLabel
          .text(function(d) { return d });


      //check if max and min overlap other values, if so, hide the values that overlap
      if (showMaxMin && (axis.orient() === 'left' || axis.orient() === 'right')) {
        g.selectAll('g') // the g's wrapping each tick
            .each(function(d,i) {
              if (scale(d) < scale.range()[1] + 10 || scale(d) > scale.range()[0] - 10) { // 10 is assuming text height is 16... if d is 0, leave it!
                if (d > 1e-10 || d < -1e-10) // accounts for minor floating point errors... though could be problematic if the scale is EXTREMELY SMALL
                  d3.select(this).remove();
                else
                  d3.select(this).select('text').remove(); // Don't remove the ZERO line!!
              }
            });
      }

      if (showMaxMin && (axis.orient() === 'top' || axis.orient() === 'bottom')) {
        var maxMinRange = [];
        wrap.selectAll('g.nv-axisMaxMin')
            .each(function(d,i) {
              if (i) // i== 1, max position
                maxMinRange.push(scale(d) - this.getBBox().width - 4)  //assuming the max and min labels are as wide as the next tick (with an extra 4 pixels just in case)
              else // i==0, min position
                maxMinRange.push(scale(d) + this.getBBox().width + 4)
            });
        g.selectAll('g') // the g's wrapping each tick
            .each(function(d,i) {
              if (scale(d) < maxMinRange[0] || scale(d) > maxMinRange[1]) {
                if (d > 1e-10 || d < -1e-10) // accounts for minor floating point errors... though could be problematic if the scale is EXTREMELY SMALL
                  d3.select(this).remove();
                else
                  d3.select(this).select('text').remove(); // Don't remove the ZERO line!!
              }
            });
      }


      //highlight zero line ... Maybe should not be an option and should just be in CSS?
      if (highlightZero)
        g.selectAll('line.tick')
          .filter(function(d) { return !parseFloat(Math.round(d*100000)/1000000) }) //this is because sometimes the 0 tick is a very small fraction, TODO: think of cleaner technique
            .classed('zero', true);

      //store old scales for use in transitions on update
      scale0 = scale.copy();

    });

    return chart;
  }


  //============================================================
  // Expose Public Variables
  //------------------------------------------------------------

  // expose chart's sub-components
  chart.axis = axis;

  d3.rebind(chart, axis, 'orient', 'tickValues', 'tickSubdivide', 'tickSize', 'tickPadding', 'tickFormat');
  d3.rebind(chart, scale, 'domain', 'range', 'rangeBand', 'rangeBands'); //these are also accessible by chart.scale(), but added common ones directly for ease of use

  chart.margin = function(_) {
    if(!arguments.length) return margin;
    margin.top    = typeof _.top    != 'undefined' ? _.top    : margin.top;
    margin.right  = typeof _.right  != 'undefined' ? _.right  : margin.right;
    margin.bottom = typeof _.bottom != 'undefined' ? _.bottom : margin.bottom;
    margin.left   = typeof _.left   != 'undefined' ? _.left   : margin.left;
    return chart;
  }

  chart.width = function(_) {
    if (!arguments.length) return width;
    width = _;
    return chart;
  };

  chart.ticks = function(_) {
    if (!arguments.length) return ticks;
    ticks = _;
    return chart;
  };

  chart.height = function(_) {
    if (!arguments.length) return height;
    height = _;
    return chart;
  };

  chart.axisLabel = function(_) {
    if (!arguments.length) return axisLabelText;
    axisLabelText = _;
    return chart;
  }

  chart.showMaxMin = function(_) {
    if (!arguments.length) return showMaxMin;
    showMaxMin = _;
    return chart;
  }

  chart.highlightZero = function(_) {
    if (!arguments.length) return highlightZero;
    highlightZero = _;
    return chart;
  }

  chart.scale = function(_) {
    if (!arguments.length) return scale;
    scale = _;
    axis.scale(scale);
    d3.rebind(chart, scale, 'domain', 'range', 'rangeBand', 'rangeBands');
    return chart;
  }

  chart.rotateYLabel = function(_) {
    if(!arguments.length) return rotateYLabel;
    rotateYLabel = _;
    return chart;
  }

  chart.rotateLabels = function(_) {
    if(!arguments.length) return rotateLabels;
    rotateLabels = _;
    return chart;
  }

  chart.staggerLabels = function(_) {
    if (!arguments.length) return staggerLabels;
    staggerLabels = _;
    return chart;
  };


  //============================================================


  return chart;
}