nv.models.scatter = function() {
  "use strict";
  //============================================================
  // Public Variables with Default Settings
  //------------------------------------------------------------

  var margin       = {top: 0, right: 0, bottom: 0, left: 0}
    , width        = 960
    , height       = 500
    , color        = nv.utils.defaultColor() // chooses color
    , id           = Math.floor(Math.random() * 100000) //Create semi-unique ID incase user doesn't select one
    , x            = d3.scale.linear()
    , y            = d3.scale.linear()
    , z            = d3.scale.linear() //linear because d3.svg.shape.size is treated as area
    , getX         = function(d) { return d.x } // accessor to get the x value
    , getY         = function(d) { return d.y } // accessor to get the y value
    , getSize      = function(d) { return d.size || 1} // accessor to get the point size
    , getShape     = function(d) { return d.shape || 'circle' } // accessor to get point shape
    , onlyCircles  = true // Set to false to use shapes
    , forceX       = [] // List of numbers to Force into the X scale (ie. 0, or a max / min, etc.)
    , forceY       = [] // List of numbers to Force into the Y scale
    , forceSize    = [] // List of numbers to Force into the Size scale
    , interactive  = true // If true, plots a voronoi overlay for advanced point intersection
    , pointKey     = null
    , pointActive  = function(d) { return !d.notActive } // any points that return false will be filtered out
    , padData      = false // If true, adds half a data points width to front and back, for lining up a line chart with a bar chart
    , padDataOuter = .1 //outerPadding to imitate ordinal scale outer padding
    , clipEdge     = false // if true, masks points within x and y scale
    , clipVoronoi  = true // if true, masks each point with a circle... can turn off to slightly increase performance
    , clipRadius   = function() { return 25 } // function to get the radius for voronoi point clips
    , xDomain      = null // Override x domain (skips the calculation from data)
    , yDomain      = null // Override y domain
    , xRange       = null // Override x range
    , yRange       = null // Override y range
    , sizeDomain   = null // Override point size domain
    , sizeRange    = null
    , singlePoint  = false
    , dispatch     = d3.dispatch('elementClick', 'elementMouseover', 'elementMouseout')
    , useVoronoi   = true
    ;

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


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

  var x0, y0, z0 // used to store previous scales
    , timeoutID
    , needsUpdate = false // Flag for when the points are visually updating, but the interactive layer is behind, to disable tooltips
    ;

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


  function chart(selection) {
    selection.each(function(data) {
      var availableWidth = width - margin.left - margin.right,
          availableHeight = height - margin.top - margin.bottom,
          container = d3.select(this);

      //add series index to each data point for reference
      data.forEach(function(series, i) {
        series.values.forEach(function(point) {
          point.series = i;
        });
      });

      //------------------------------------------------------------
      // Setup Scales

      // remap and flatten the data for use in calculating the scales' domains
      var seriesData = (xDomain && yDomain && sizeDomain) ? [] : // if we know xDomain and yDomain and sizeDomain, no need to calculate.... if Size is constant remember to set sizeDomain to speed up performance
            d3.merge(
              data.map(function(d) {
                return d.values.map(function(d,i) {
                  return { x: getX(d,i), y: getY(d,i), size: getSize(d,i) }
                })
              })
            );

      x   .domain(xDomain || d3.extent(seriesData.map(function(d) { return d.x; }).concat(forceX)))

      if (padData && data[0])
        x.range(xRange || [(availableWidth * padDataOuter +  availableWidth) / (2 *data[0].values.length), availableWidth - availableWidth * (1 + padDataOuter) / (2 * data[0].values.length)  ]);
        //x.range([availableWidth * .5 / data[0].values.length, availableWidth * (data[0].values.length - .5)  / data[0].values.length ]);
      else
        x.range(xRange || [0, availableWidth]);

      y   .domain(yDomain || d3.extent(seriesData.map(function(d) { return d.y }).concat(forceY)))
          .range(yRange || [availableHeight, 0]);

      z   .domain(sizeDomain || d3.extent(seriesData.map(function(d) { return d.size }).concat(forceSize)))
          .range(sizeRange || [16, 256]);

      // If scale's domain don't have a range, slightly adjust to make one... so a chart can show a single data point
      if (x.domain()[0] === x.domain()[1] || y.domain()[0] === y.domain()[1]) singlePoint = true;
      if (x.domain()[0] === x.domain()[1])
        x.domain()[0] ?
            x.domain([x.domain()[0] - x.domain()[0] * 0.01, x.domain()[1] + x.domain()[1] * 0.01])
          : x.domain([-1,1]);

      if (y.domain()[0] === y.domain()[1])
        y.domain()[0] ?
            y.domain([y.domain()[0] - y.domain()[0] * 0.01, y.domain()[1] + y.domain()[1] * 0.01])
          : y.domain([-1,1]);

      if ( isNaN(x.domain()[0])) {
          x.domain([-1,1]);
      }

      if ( isNaN(y.domain()[0])) {
          y.domain([-1,1]);
      }


      x0 = x0 || x;
      y0 = y0 || y;
      z0 = z0 || z;

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


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

      var wrap = container.selectAll('g.nv-wrap.nv-scatter').data([data]);
      var wrapEnter = wrap.enter().append('g').attr('class', 'nvd3 nv-wrap nv-scatter nv-chart-' + id + (singlePoint ? ' nv-single-point' : ''));
      var defsEnter = wrapEnter.append('defs');
      var gEnter = wrapEnter.append('g');
      var g = wrap.select('g');

      gEnter.append('g').attr('class', 'nv-groups');
      gEnter.append('g').attr('class', 'nv-point-paths');

      wrap.attr('transform', 'translate(' + margin.left + ',' + margin.top + ')');

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


      defsEnter.append('clipPath')
          .attr('id', 'nv-edge-clip-' + id)
        .append('rect');

      wrap.select('#nv-edge-clip-' + id + ' rect')
          .attr('width', availableWidth)
          .attr('height', availableHeight);

      g   .attr('clip-path', clipEdge ? 'url(#nv-edge-clip-' + id + ')' : '');


      function updateInteractiveLayer() {

        if (!interactive) return false;

        var eventElements;

        var vertices = d3.merge(data.map(function(group, groupIndex) {
            return group.values
              .map(function(point, pointIndex) {
                // *Adding noise to make duplicates very unlikely
                // *Injecting series and point index for reference
                /* *Adding a 'jitter' to the points, because there's an issue in d3.geom.voronoi.
                */
                var pX = getX(point,pointIndex);
                var pY = getY(point,pointIndex);

                return [x(pX)+ Math.random() * 1e-7,
                        y(pY)+ Math.random() * 1e-7,
                        groupIndex,
                        pointIndex, point]; //temp hack to add noise untill I think of a better way so there are no duplicates
              })
              .filter(function(pointArray, pointIndex) {
                return pointActive(pointArray[4], pointIndex); // Issue #237.. move filter to after map, so pointIndex is correct!
              })
          })
        );



        //inject series and point index for reference into voronoi
        if (useVoronoi === true) {

          if (clipVoronoi) {
            var pointClipsEnter = wrap.select('defs').selectAll('.nv-point-clips')
                .data([id])
              .enter();

            pointClipsEnter.append('clipPath')
                  .attr('class', 'nv-point-clips')
                  .attr('id', 'nv-points-clip-' + id);

            var pointClips = wrap.select('#nv-points-clip-' + id).selectAll('circle')
                .data(vertices);
            pointClips.enter().append('circle')
                .attr('r', clipRadius);
            pointClips.exit().remove();
            pointClips
                .attr('cx', function(d) { return d[0] })
                .attr('cy', function(d) { return d[1] });

            wrap.select('.nv-point-paths')
                .attr('clip-path', 'url(#nv-points-clip-' + id + ')');
          }


          if(vertices.length) {
            // Issue #283 - Adding 2 dummy points to the voronoi b/c voronoi requires min 3 points to work
            vertices.push([x.range()[0] - 20, y.range()[0] - 20, null, null]);
            vertices.push([x.range()[1] + 20, y.range()[1] + 20, null, null]);
            vertices.push([x.range()[0] - 20, y.range()[0] + 20, null, null]);
            vertices.push([x.range()[1] + 20, y.range()[1] - 20, null, null]);
          }

          var bounds = d3.geom.polygon([
              [-10,-10],
              [-10,height + 10],
              [width + 10,height + 10],
              [width + 10,-10]
          ]);

          var voronoi = d3.geom.voronoi(vertices).map(function(d, i) {
              return {
                'data': bounds.clip(d),
                'series': vertices[i][2],
                'point': vertices[i][3]
              }
            });


          var pointPaths = wrap.select('.nv-point-paths').selectAll('path')
              .data(voronoi);
          pointPaths.enter().append('path')
              .attr('class', function(d,i) { return 'nv-path-'+i; });
          pointPaths.exit().remove();
          pointPaths
              .attr('d', function(d) {
                if (d.data.length === 0)
                    return 'M 0 0'
                else
                    return 'M' + d.data.join('L') + 'Z';
              });

          var mouseEventCallback = function(d,mDispatch) {
                if (needsUpdate) return 0;
                var series = data[d.series];
                if (typeof series === 'undefined') return;

                var point  = series.values[d.point];

                mDispatch({
                  point: point,
                  series: series,
                  pos: [x(getX(point, d.point)) + margin.left, y(getY(point, d.point)) + margin.top],
                  seriesIndex: d.series,
                  pointIndex: d.point
                });
          };

          pointPaths
              .on('click', function(d) {
                mouseEventCallback(d, dispatch.elementClick);
              })
              .on('mouseover', function(d) {
                mouseEventCallback(d, dispatch.elementMouseover);
              })
              .on('mouseout', function(d, i) {
                mouseEventCallback(d, dispatch.elementMouseout);
              });


        } else {
          /*
          // bring data in form needed for click handlers
          var dataWithPoints = vertices.map(function(d, i) {
              return {
                'data': d,
                'series': vertices[i][2],
                'point': vertices[i][3]
              }
            });
           */

          // add event handlers to points instead voronoi paths
          wrap.select('.nv-groups').selectAll('.nv-group')
            .selectAll('.nv-point')
              //.data(dataWithPoints)
              //.style('pointer-events', 'auto') // recativate events, disabled by css
              .on('click', function(d,i) {
                //nv.log('test', d, i);
                if (needsUpdate || !data[d.series]) return 0; //check if this is a dummy point
                var series = data[d.series],
                    point  = series.values[i];

                dispatch.elementClick({
                  point: point,
                  series: series,
                  pos: [x(getX(point, i)) + margin.left, y(getY(point, i)) + margin.top],
                  seriesIndex: d.series,
                  pointIndex: i
                });
              })
              .on('mouseover', function(d,i) {
                if (needsUpdate || !data[d.series]) return 0; //check if this is a dummy point
                var series = data[d.series],
                    point  = series.values[i];

                dispatch.elementMouseover({
                  point: point,
                  series: series,
                  pos: [x(getX(point, i)) + margin.left, y(getY(point, i)) + margin.top],
                  seriesIndex: d.series,
                  pointIndex: i
                });
              })
              .on('mouseout', function(d,i) {
                if (needsUpdate || !data[d.series]) return 0; //check if this is a dummy point
                var series = data[d.series],
                    point  = series.values[i];

                dispatch.elementMouseout({
                  point: point,
                  series: series,
                  seriesIndex: d.series,
                  pointIndex: i
                });
              });
          }

          needsUpdate = false;
      }

      needsUpdate = true;

      var groups = wrap.select('.nv-groups').selectAll('.nv-group')
          .data(function(d) { return d }, function(d) { return d.key });
      groups.enter().append('g')
          .style('stroke-opacity', 1e-6)
          .style('fill-opacity', 1e-6);
      groups.exit()
          .remove();
      groups
          .attr('class', function(d,i) { return 'nv-group nv-series-' + i })
          .classed('hover', function(d) { return d.hover });
      groups
          .transition()
          .style('fill', function(d,i) { return color(d, i) })
          .style('stroke', function(d,i) { return color(d, i) })
          .style('stroke-opacity', 1)
          .style('fill-opacity', .5);


      if (onlyCircles) {

        var points = groups.selectAll('circle.nv-point')
            .data(function(d) { return d.values }, pointKey);
        points.enter().append('circle')
            .style('fill', function (d,i) { return d.color })
            .style('stroke', function (d,i) { return d.color })
            .attr('cx', function(d,i) { return nv.utils.NaNtoZero(x0(getX(d,i))) })
            .attr('cy', function(d,i) { return nv.utils.NaNtoZero(y0(getY(d,i))) })
            .attr('r', function(d,i) { return Math.sqrt(z(getSize(d,i))/Math.PI) });
        points.exit().remove();
        groups.exit().selectAll('path.nv-point').transition()
            .attr('cx', function(d,i) { return nv.utils.NaNtoZero(x(getX(d,i))) })
            .attr('cy', function(d,i) { return nv.utils.NaNtoZero(y(getY(d,i))) })
            .remove();
        points.each(function(d,i) {
          d3.select(this)
            .classed('nv-point', true)
            .classed('nv-point-' + i, true)
            .classed('hover',false)
            ;
        });
        points.transition()
            .attr('cx', function(d,i) { return nv.utils.NaNtoZero(x(getX(d,i))) })
            .attr('cy', function(d,i) { return nv.utils.NaNtoZero(y(getY(d,i))) })
            .attr('r', function(d,i) { return Math.sqrt(z(getSize(d,i))/Math.PI) });

      } else {

        var points = groups.selectAll('path.nv-point')
            .data(function(d) { return d.values });
        points.enter().append('path')
            .style('fill', function (d,i) { return d.color })
            .style('stroke', function (d,i) { return d.color })
            .attr('transform', function(d,i) {
              return 'translate(' + x0(getX(d,i)) + ',' + y0(getY(d,i)) + ')'
            })
            .attr('d',
              d3.svg.symbol()
                .type(getShape)
                .size(function(d,i) { return z(getSize(d,i)) })
            );
        points.exit().remove();
        groups.exit().selectAll('path.nv-point')
            .transition()
            .attr('transform', function(d,i) {
              return 'translate(' + x(getX(d,i)) + ',' + y(getY(d,i)) + ')'
            })
            .remove();
        points.each(function(d,i) {
          d3.select(this)
            .classed('nv-point', true)
            .classed('nv-point-' + i, true)
            .classed('hover',false)
            ;
        });
        points.transition()
            .attr('transform', function(d,i) {
              //nv.log(d,i,getX(d,i), x(getX(d,i)));
              return 'translate(' + x(getX(d,i)) + ',' + y(getY(d,i)) + ')'
            })
            .attr('d',
              d3.svg.symbol()
                .type(getShape)
                .size(function(d,i) { return z(getSize(d,i)) })
            );
      }


      // Delay updating the invisible interactive layer for smoother animation
      clearTimeout(timeoutID); // stop repeat calls to updateInteractiveLayer
      timeoutID = setTimeout(updateInteractiveLayer, 300);
      //updateInteractiveLayer();

      //store old scales for use in transitions on update
      x0 = x.copy();
      y0 = y.copy();
      z0 = z.copy();

    });

    return chart;
  }


  //============================================================
  // Event Handling/Dispatching (out of chart's scope)
  //------------------------------------------------------------
  chart.clearHighlights = function() {
      //Remove the 'hover' class from all highlighted points.
      d3.selectAll(".nv-chart-" + id + " .nv-point.hover").classed("hover",false);
  };

  chart.highlightPoint = function(seriesIndex,pointIndex,isHoverOver) {
      d3.select(".nv-chart-" + id + " .nv-series-" + seriesIndex + " .nv-point-" + pointIndex)
          .classed("hover",isHoverOver);
  };


  dispatch.on('elementMouseover.point', function(d) {
     if (interactive) chart.highlightPoint(d.seriesIndex,d.pointIndex,true);
  });

  dispatch.on('elementMouseout.point', function(d) {
     if (interactive) chart.highlightPoint(d.seriesIndex,d.pointIndex,false);
  });

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


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

  chart.dispatch = dispatch;
  chart.options = nv.utils.optionsFunc.bind(chart);

  chart.x = function(_) {
    if (!arguments.length) return getX;
    getX = d3.functor(_);
    return chart;
  };

  chart.y = function(_) {
    if (!arguments.length) return getY;
    getY = d3.functor(_);
    return chart;
  };

  chart.size = function(_) {
    if (!arguments.length) return getSize;
    getSize = d3.functor(_);
    return chart;
  };

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  chart.useVoronoi= function(_) {
    if (!arguments.length) return useVoronoi;
    useVoronoi = _;
    if (useVoronoi === false) {
        clipVoronoi = false;
    }
    return chart;
  };

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

  chart.color = function(_) {
    if (!arguments.length) return color;
    color = nv.utils.getColor(_);
    return chart;
  };

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

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

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

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

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


  return chart;
}