Highcharts - Stepped lines

Trying to show better/worse measures where +1 = getting better, -1 = getting worse

by mark47

HTML

<script src="http://code.highcharts.com/highcharts.js"></script>
<div id="container" style="height: 400px"></div>
<br /><br />
<div id="container" style="height: 400px"></div>

CSS

body {
    font-family: Arial, Verdana, sans-serif;
}

JavaScript

$(function () {
    $('#container').highcharts({
        colors: ['rgba(100,100,255,0.8)', '#0066FF', '#00CCFF'],
        title: {
            text: 'Symptoms Over Time'
        },
        xAxis: {
            categories: ['Start', '#1', '#2', '#3', '#4', '#5', '#6', '#7']
        },
        yAxis: {
            min: -5,
            max: 5,
            title: {
                enabled: false
            },
            labels: {
                formatter: function () {
                    if (this.value == 2.5) {
                        return 'Getting Better';
                    } else if (this.value == -2.5) {
                        return 'Getting Worse'
                    }
                }
            }
        },
        series: [{
            data: [0, 1, 2, 3, 3, 4, 3, 2],
            step: 'center',
            name: 'Pain'
        }, {
            data: [0, 0, -1, -1, -2, -3, -2, -1],
            step: 'left',
            name: 'Redness'
        }, {
            data: [0, 1, 2, 3, null, null, null, null],
            step: 'left',
            name: 'Warmth'
        }],
        plotOptions: {
            series: {
                lineWidth: 1,
                marker: {
                    enabled: false
                },
                states: {
                    hover: {
                        lineWidthPlus: 3
                    }
                }
            }
        }
    });
});