How to draw horizontal line in NVD3

HTML

<script src="//cdnjs.cloudflare.com/ajax/libs/nvd3/1.1.15-beta/nv.d3.min.js"></script>
<link rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/nvd3/1.1.15-beta/nv.d3.css">
<div id="chart">
    <svg></svg>
</div>

CSS

#chart svg {
    height: 400px;
}

JavaScript

function getData(groups, points) {
    var data = [],
        shapes = ['circle', 'cross', 'triangle-up', 'triangle-down', 'diamond', 'square'],
        random = d3.random.normal();

    for (i = 0; i < groups; i++) {
        data.push({
            key: 'Group ' + i,
            values: []
        });

        for (j = 0; j < points; j++) {
            data[i].values.push({
                x: random() + 3,
                y: Math.floor(Math.random() * 33),
                size: Math.random()
                //, shape: shapes[j % 6]
            });
        }
    }

    return data;
}

//nv.addGraph(function() {
var chart = nv.models.scatterChart()
    .showDistX(true)
    .showDistY(true)
    .xDomain([0, 3])

    .color(d3.scale.category10().range());

chart.xAxis.tickFormat(d3.format('.02f'));
chart.yAxis.tickFormat(d3.format('.02f'));
chart.yAxis.tickValues(['2', '4', '8', '16', '32']);

var data = getData(4, 40);

d3.select('#chart svg')
    .datum(getData(4, 40))
    .transition().duration(500)
    .call(chart);

var line = d3.select('#chart svg')
    .append('line')
    .attr({
        x1: 75 + chart.xAxis.scale()(0),
        y1: 30 + chart.yAxis.scale()(16),
        x2: 75 + chart.xAxis.scale()(3),
        y2: 30 + chart.yAxis.scale()(16)
    })
    .style("stroke", "#000");

nv.utils.windowResize(function(){
    chart.update();
    line.attr({
        x1: 75 + chart.xAxis.scale()(0),
        y1: 30 + chart.yAxis.scale()(16),
        x2: 75 + chart.xAxis.scale()(3),
        y2: 30 + chart.yAxis.scale()(16)
    })
    
});


//return chart;
//});