Chart.js: Drawing horizontal Limit Lines - Javascript Chart.js

Javascript examples for Chart.js:Line Chart

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Description

Chart.js: Drawing horizontal Limit Lines

Demo Code

ResultView the demo in separate window 

<html>
   <head> 
      <title>line chart with ChartJS</title> 
      <meta name="viewport" content="width=device-width, initial-scale=1"> 
      <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.0.0-beta/Chart.js"></script> 
      <script type="text/javascript">
    window.onload=function(){//from  w  w w  . j  ava2 s .  c  o  m
var originalLineDraw = Chart.controllers.line.prototype.draw;
Chart.helpers.extend(Chart.controllers.line.prototype, {
  draw: function() {
    originalLineDraw.apply(this, arguments);
    var chart = this.chart;
    var ctx = chart.chart.ctx;
    var index = chart.config.data.lineAtIndex;
    if (index) {
      var xaxis = chart.scales['x-axis-0'];
      var yaxis = chart.scales['y-axis-0'];
      ctx.save();
      ctx.beginPath();
      ctx.moveTo(xaxis.getPixelForValue(undefined, index), yaxis.top);
      ctx.strokeStyle = '#ff0000';
      ctx.lineTo(xaxis.getPixelForValue(undefined, index), yaxis.bottom);
      ctx.stroke();
      ctx.restore();
    }
  }
});
var config = {
  type: 'line',
  data: {
    labels: ["January", "February", "March", "April", "May", "June", "July"],
    datasets: [{
      label: "My First dataset",
      data: [65, 0, 80, 81, 56, 85, 40],
      fill: false
    }],
    lineAtIndex: 2
  }
};
var ctx = document.getElementById("myChart").getContext("2d");
new Chart(ctx, config);
    }

      </script> 
   </head> 
   <body> 
      <canvas id="myChart"></canvas>  
   </body>
</html>

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