title: Draw horizontal line on chart in chart.js on v2
body: <p>I have drawn a line chart using chart.js. For the labels and datasets i am getting values from the database. I am new to chart.js and its very powerful library, yet i am unable to completely understand it. I want to draw multiples horizontal lines. Like where if mean of dataset, standard deviation and min and max. I have tried the question here in stackoverflow but these are giving errors or may be i am not able to understand the working. This is my chart.js code</p>
  
  <pre><code>function display_graph(id, label, data) {
  var ctx = document.getElementById(id);
  var data = {
      labels: data.labels,
      datasets: [
          {
              label: label,
              fill: false,
              lineTension: 0.1,
              backgroundColor: "rgba(75,192,192,0.4)",
              borderColor: "rgba(75,192,192,1)",
              borderCapStyle: 'butt',
              borderDash: [],
              borderDashOffset: 0.0,
              borderWidth: 1,
              borderJoinStyle: 'miter',
              pointBorderColor: "rgba(75,192,192,1)",
              pointBackgroundColor: "#fff",
              pointBorderWidth: 1,
              pointHoverRadius: 5,
              pointHoverBackgroundColor: "rgba(75,192,192,1)",
              pointHoverBorderColor: "rgba(220,220,220,1)",
              pointHoverBorderWidth: 2,
              pointRadius: 1,
              pointHitRadius: 10,
              data: data.assay_value,
              spanGaps: false
          }
      ]
  };
  
  //options
  var options = {
      responsive: true,
      title: {
          display: true,
          position: "top",
          text: label,
          fontSize: 18,
          fontColor: "#111"
      },
      legend: {
          display: true,
          position: "bottom",
          labels: {
              fontColor: "#333",
              fontSize: 16
          }
      }
  };
  var Blanks_Chart=null;
  Blanks_Chart = new Chart(ctx, {
      type: 'line',
      data: data,
      options: options
  });}
  </code></pre>