line chart with ChartJS

HTML

<script src="http://www.chartjs.org/assets/Chart.min.js"></script>
<canvas id="myChart" width="800" height="400"></canvas>

JavaScript

Chart.types.Line.extend({
  name: "LineAlt",
  initialize: function (data) {
    this.chart.height -= 30;

    Chart.types.Line.prototype.initialize.apply(this, arguments);

    var ctx = this.chart.ctx;
    ctx.save();
    // text alignment and color
    ctx.textAlign = "center";
    ctx.textBaseline = "bottom";
    ctx.fillStyle = this.options.scaleFontColor;
    // position
    var x = this.chart.width / 2;
    var y = this.chart.height + 15 + 5;
    // change origin
    ctx.translate(x, y)
    ctx.fillText("My x axis label", 0, 0);
    ctx.restore();
  }
});


var data = {
  labels: ["January", "February", "March", "April", "May", "June", "July", "August", "September"],
  xAxisLabel: "",
  datasets: [
    {
      label: "My First dataset",
      fillColor: "rgba(220,220,220,0.2)",
      strokeColor: "rgba(220,220,220,1)",
      pointColor: "rgba(220,220,220,1)",
      pointStrokeColor: "#fff",
      pointHighlightFill: "#fff",
      pointHighlightStroke: "rgba(220,220,220,1)",
      data: [28, 48, 40, 19, 86, 27, 90, 24, 32]
    }
  ]
};

var ctx = document.getElementById('myChart').getContext('2d');
new Chart(ctx).LineAlt(data);