nv.models.multiBar = function() {
    "use strict";

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

    var margin = {top: 0, right: 0, bottom: 0, left: 0}
        , width = 960
        , height = 500
        , x = d3.scale.ordinal()
        , y = d3.scale.linear()
        , id = Math.floor(Math.random() * 10000) //Create semi-unique ID in case user doesn't select one
        , container = null
        , getX = function(d) { return d.x }
        , getY = function(d) { return d.y }
        , getYerr = function(d) { return d.yErr }
        , forceY = [0] // 0 is forced by default.. this makes sense for the majority of bar graphs... user can always do chart.forceY([]) to remove
        , clipEdge = true
        , stacked = false
        , stackOffset = 'zero' // options include 'silhouette', 'wiggle', 'expand', 'zero', or a custom function
        , color = nv.utils.defaultColor()
        , errorBarColor = nv.utils.defaultColor()
        , hideable = false
        , barColor = null // adding the ability to set the color for each rather than the whole group
        , disabled // used in conjunction with barColor to communicate from multiBarHorizontalChart what series are disabled
        , duration = 500
        , xDomain
        , yDomain
        , xRange
        , yRange
        , groupSpacing = 0.1
        , dispatch = d3.dispatch('chartClick', 'elementClick', 'elementDblClick', 'elementMouseover', 'elementMouseout', 'elementMousemove', 'renderEnd')
        ;

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

    var x0, y0 //used to store previous scales
        , renderWatch = nv.utils.renderWatch(dispatch, duration)
        ;

    var last_datalength = 0;

    function chart(selection) {
        renderWatch.reset();
        selection.each(function(data) {
            var availableWidth = width - margin.left - margin.right,
                availableHeight = height - margin.top - margin.bottom;

            container = d3.select(this);
            nv.utils.initSVG(container);
            var nonStackableCount = 0;
            // This function defines the requirements for render complete
            var endFn = function(d, i) {
                if (d.series === data.length - 1 && i === data[0].values.length - 1)
                    return true;
                return false;
            };

            if(hideable && data.length) hideable = [{
                values: data[0].values.map(function(d) {
                        return {
                            x: d.x,
                            y: 0,
                            series: d.series,
                            size: 0.01
                        };}
                )}];

            if (stacked) {
                var parsed = d3.layout.stack()
                    .offset(stackOffset)
                    .values(function(d){ return d.values })
                    .y(getY)
                (!data.length && hideable ? hideable : data);

                parsed.forEach(function(series, i){
                    // if series is non-stackable, use un-parsed data
                    if (series.nonStackable) {
                        data[i].nonStackableSeries = nonStackableCount++; 
                        parsed[i] = data[i];
                    } else {
                        // don't stack this seires on top of the nonStackable seriees 
                        if (i > 0 && parsed[i - 1].nonStackable){
                            parsed[i].values.map(function(d,j){
                                d.y0 -= parsed[i - 1].values[j].y;
                                d.y1 = d.y0 + d.y;
                            });
                        }
                    }
                });
                data = parsed;
            }
            //add series index and key to each data point for reference
            data.forEach(function(series, i) {
                series.values.forEach(function(point) {
                    point.series = i;
                    point.key = series.key;
                });
            });

            // HACK for negative value stacking
            if (stacked) {
                data[0].values.map(function(d,i) {
                    var posBase = 0, negBase = 0;
                    data.map(function(d, idx) {
                        if (!data[idx].nonStackable) {
                            var f = d.values[i]
                            f.size = Math.abs(f.y);
                            if (f.y<0)  {
                                f.y1 = negBase;
                                negBase = negBase - f.size;
                            } else
                            {
                                f.y1 = f.size + posBase;
                                posBase = posBase + f.size;
                            }
                        }
                        
                    });
                });
            }
            // Setup Scales
            // remap and flatten the data for use in calculating the scales' domains
            var seriesData = (xDomain && yDomain) ? [] : // if we know xDomain and yDomain, no need to calculate
                data.map(function(d, idx) {
                    return d.values.map(function(d,i) {
                        return { x: getX(d,i), y: getY(d,i), y0: d.y0, y1: d.y1, idx:idx, yErr: getYerr(d,i)}
                    })
                });

            x.domain(xDomain || d3.merge(seriesData).map(function(d) { return d.x }))
                .rangeBands(xRange || [0, availableWidth], groupSpacing);

            y.domain(yDomain || d3.extent(d3.merge(
                d3.merge(seriesData).map(function(d) {
                    var domain = d.y;
                    // increase the domain range if this series is stackable
                    if (stacked && !data[d.idx].nonStackable) {
                        if (d.y > 0){
                            domain = d.y1
                        } else {
                            domain = d.y1 + d.y
                        }
                    }
                    var yerr = d.yErr;
                    if (yerr) {
                        if (yerr.length) {
                            return [domain + yerr[0], domain + yerr[1]];
                        } else {
                            yerr = Math.abs(yerr)
                            return [domain - yerr, domain + yerr];
                        }
                    } else {
                        return [domain];
                    }
                })).concat(forceY)))
            .range(yRange || [availableHeight, 0]);

            // 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])
                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]);

            x0 = x0 || x;
            y0 = y0 || y;

            // Setup containers and skeleton of chart
            var wrap = container.selectAll('g.nv-wrap.nv-multibar').data([data]);
            var wrapEnter = wrap.enter().append('g').attr('class', 'nvd3 nv-wrap nv-multibar');
            var defsEnter = wrapEnter.append('defs');
            var gEnter = wrapEnter.append('g');
            var g = wrap.select('g');

            gEnter.append('g').attr('class', 'nv-groups');
            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 + ')' : '');

            var groups = wrap.select('.nv-groups').selectAll('.nv-group')
                .data(function(d) { return d }, function(d,i) { return i });
            groups.enter().append('g')
                .style('stroke-opacity', 1e-6)
                .style('fill-opacity', 1e-6);

            var exitTransition = renderWatch
                .transition(groups.exit().selectAll('g.nv-bar'), 'multibarExit', Math.min(100, duration))
                .attr('y', function(d, i, j) {
                    var yVal = y0(0) || 0;
                    if (stacked) {
                        if (data[d.series] && !data[d.series].nonStackable) {
                            yVal = y0(d.y0);
                        }
                    }
                    return yVal;
                })
                .attr('height', 0)
                .remove();
            if (exitTransition.delay)
                exitTransition.delay(function(d,i) {
                    var delay = i * (duration / (last_datalength + 1)) - i;
                    return delay;
                });
            groups
                .attr('class', function(d,i) { return 'nv-group nv-series-' + i })
                .classed('hover', function(d) { return d.hover })
                .style('fill', function(d,i){ return color(d, i) })
                .style('stroke', function(d,i){ return color(d, i) });
            groups
                .style('stroke-opacity', 1)
                .style('fill-opacity', 0.75);

            var bars = groups.selectAll('g.nv-bar')
                .data(function(d) { return (hideable && !data.length) ? hideable.values : d.values });
            bars.exit().remove();

            var barsEnter = bars.enter().append('g')
                    .attr('class', function(d,i) { return getY(d,i) < 0 ? 'nv-bar negative' : 'nv-bar positive'})
                    .attr('transform', function(d,i,j) {
                        var _x = stacked && !data[j].nonStackable ? 0 : (j * x.rangeBand() / data.length );
                        var _y = y0(stacked && !data[j].nonStackable ? d.y0 : 0) || 0;
                        return 'translate(' + _x + ',' + _y + ')';
                    })
                ;

            barsEnter.append('rect')
                    .attr('height', 0)
                    .attr('width', function(d,i,j) { return x.rangeBand() / (stacked && !data[j].nonStackable ? 1 : data.length) })
                    .style('fill', function(d,i,j){ return color(d, j, i);  })
                    .style('stroke', function(d,i,j){ return color(d, j, i); })
                ;
            bars
                .on('mouseover', function(d,i) { //TODO: figure out why j works above, but not here
                    d3.select(this).classed('hover', true);
                    dispatch.elementMouseover({
                        data: d,
                        index: i,
                        color: d3.select(this).style("fill")
                    });
                })
                .on('mouseout', function(d,i) {
                    d3.select(this).classed('hover', false);
                    dispatch.elementMouseout({
                        data: d,
                        index: i,
                        color: d3.select(this).style("fill")
                    });
                })
                .on('mousemove', function(d,i) {
                    dispatch.elementMousemove({
                        data: d,
                        index: i,
                        color: d3.select(this).style("fill")
                    });
                })
                .on('click', function(d,i) {
                    dispatch.elementClick({
                        data: d,
                        index: i,
                        color: d3.select(this).style("fill")
                    });
                    d3.event.stopPropagation();
                })
                .on('dblclick', function(d,i) {
                    dispatch.elementDblClick({
                        data: d,
                        index: i,
                        color: d3.select(this).style("fill")
                    });
                    d3.event.stopPropagation();
                });

            if (getYerr(data[0].values[0], 0)) {
                barsEnter.append('polyline');

                bars.select('polyline')
                    .attr('fill', 'none')
                    .attr('stroke', function(d, i, j) { return errorBarColor(d, j, i); })
                    .attr('points', function(d,i) {
                        var yerr = getYerr(d,i)
                            , mid = 0.8 * x.rangeBand() / ((stacked ? 1 : data.length) * 2);
                        yerr = yerr.length ? yerr : [-Math.abs(yerr), Math.abs(yerr)];
                        yerr = yerr.map(function(e) { return y(e) - y(0); });
                        var a = [[-mid, yerr[0]], [mid, yerr[0]], [0, yerr[0]], [0, yerr[1]], [-mid, yerr[1]], [mid, yerr[1]]];
                        return a.map(function (path) { return path.join(',') }).join(' ');
                    })
                    .attr('transform', function(d, i) {
                        var xOffset = x.rangeBand() / ((stacked ? 1 : data.length) * 2);
                        var yOffset = getY(d,i) < 0 ? y(getY(d, i)) - y(0) : 0;
                        return 'translate(' + xOffset + ', ' + yOffset + ')';
                    })
            }

            bars
                .attr('class', function(d,i) { return getY(d,i) < 0 ? 'nv-bar negative' : 'nv-bar positive'})

            if (barColor) {
                if (!disabled) disabled = data.map(function() { return true });
                bars.select('rect')
                    .style('fill', function(d,i,j) { return d3.rgb(barColor(d,i)).darker(  disabled.map(function(d,i) { return i }).filter(function(d,i){ return !disabled[i]  })[j]   ).toString(); })
                    .style('stroke', function(d,i,j) { return d3.rgb(barColor(d,i)).darker(  disabled.map(function(d,i) { return i }).filter(function(d,i){ return !disabled[i]  })[j]   ).toString(); });
            }

            var barSelection =
                bars.watchTransition(renderWatch, 'multibar', Math.min(250, duration))
                    .delay(function(d,i) {
                        return i * duration / data[0].values.length;
                    });
            if (stacked){
                barSelection
                    .attr('transform', function(d,i,j) {
                        var yVal = 0;
                        // if stackable, stack it on top of the previous series
                        if (!data[j].nonStackable) {
                            yVal = y(d.y1);
                        } else {
                            if (getY(d,i) < 0){
                                yVal = y(0);
                            } else {
                                if (y(0) - y(getY(d,i)) < -1){
                                    yVal = y(0) - 1;
                                } else {
                                    yVal = y(getY(d, i)) || 0;
                                }
                            }
                        }
                        var width = 0;
                        if (data[j].nonStackable) {
                            width = d.series * x.rangeBand() / data.length;
                            if (data.length !== nonStackableCount){
                                width = data[j].nonStackableSeries * x.rangeBand()/(nonStackableCount*2); 
                            }
                        }
                        var xVal = width + x(getX(d, i));
                        return 'translate(' + xVal + ',' + yVal + ')';
                    })
                    .select('rect')
                    .attr('height', function(d,i,j) {
                        if (!data[j].nonStackable) {
                            return Math.max(Math.abs(y(d.y+d.y0) - y(d.y0)), 1);
                        } else {
                            return Math.max(Math.abs(y(getY(d,i)) - y(0)),1) || 0;
                        }
                    })
                    .attr('width', function(d,i,j){
                        if (!data[j].nonStackable) {
                            return x.rangeBand();
                        } else {
                            // if all series are nonStacable, take the full width
                            var width = (x.rangeBand() / nonStackableCount);
                            // otherwise, nonStackable graph will be only taking the half-width 
                            // of the x rangeBand
                            if (data.length !== nonStackableCount) {
                                width = x.rangeBand()/(nonStackableCount*2);
                            }
                            return width;
                        }
                    });
            }
            else {
                barSelection.attr('transform', function(d,i) {
                    var xVal = d.series * x.rangeBand() / data.length + x(getX(d, i));
                    var yVal = getY(d,i) < 0 ?
                            y(0) :
                                y(0) - y(getY(d,i)) < 1 ?
                            y(0) - 1 :
                            y(getY(d,i)) || 0;
                    return 'translate(' + xVal + ',' + yVal + ')';
                    })
                    .select('rect')
                    .attr('width', x.rangeBand() / data.length)
                    .attr('height', function(d,i) {
                        return Math.max(Math.abs(y(getY(d,i)) - y(0)),1) || 0;
                    });
            }

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

            // keep track of the last data value length for transition calculations
            if (data[0] && data[0].values) {
                last_datalength = data[0].values.length;
            }

        });

        renderWatch.renderEnd('multibar immediate');

        return chart;
    }

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

    chart.dispatch = dispatch;

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

    chart._options = Object.create({}, {
        // simple options, just get/set the necessary values
        width:   {get: function(){return width;}, set: function(_){width=_;}},
        height:  {get: function(){return height;}, set: function(_){height=_;}},
        x:       {get: function(){return getX;}, set: function(_){getX=_;}},
        y:       {get: function(){return getY;}, set: function(_){getY=_;}},
        yErr:       {get: function(){return getYerr;}, set: function(_){getYerr=_;}},
        xScale:  {get: function(){return x;}, set: function(_){x=_;}},
        yScale:  {get: function(){return y;}, set: function(_){y=_;}},
        xDomain: {get: function(){return xDomain;}, set: function(_){xDomain=_;}},
        yDomain: {get: function(){return yDomain;}, set: function(_){yDomain=_;}},
        xRange:  {get: function(){return xRange;}, set: function(_){xRange=_;}},
        yRange:  {get: function(){return yRange;}, set: function(_){yRange=_;}},
        forceY:  {get: function(){return forceY;}, set: function(_){forceY=_;}},
        stacked: {get: function(){return stacked;}, set: function(_){stacked=_;}},
        stackOffset: {get: function(){return stackOffset;}, set: function(_){stackOffset=_;}},
        clipEdge:    {get: function(){return clipEdge;}, set: function(_){clipEdge=_;}},
        disabled:    {get: function(){return disabled;}, set: function(_){disabled=_;}},
        id:          {get: function(){return id;}, set: function(_){id=_;}},
        hideable:    {get: function(){return hideable;}, set: function(_){hideable=_;}},
        groupSpacing:{get: function(){return groupSpacing;}, set: function(_){groupSpacing=_;}},

        // options that require extra logic in the setter
        margin: {get: function(){return margin;}, set: function(_){
            margin.top    = _.top    !== undefined ? _.top    : margin.top;
            margin.right  = _.right  !== undefined ? _.right  : margin.right;
            margin.bottom = _.bottom !== undefined ? _.bottom : margin.bottom;
            margin.left   = _.left   !== undefined ? _.left   : margin.left;
        }},
        duration: {get: function(){return duration;}, set: function(_){
            duration = _;
            renderWatch.reset(duration);
        }},
        color:  {get: function(){return color;}, set: function(_){
            color = nv.utils.getColor(_);
        }},
        barColor:  {get: function(){return barColor;}, set: function(_){
            barColor = _ ? nv.utils.getColor(_) : null;
        }},
        errorBarColor:  {get: function(){return errorBarColor;}, set: function(_){
            errorBarColor = _ ? nv.utils.getColor(_) : null;
        }}
    });

    nv.utils.initOptions(chart);

    return chart;
};
