Adding Datapoint from user input - CanvasJS JavaScript Charts

Adding Datapoint from user input - CanvasJS JavaScript Charts

HTML

<script src="http://canvasjs.com/assets/script/canvasjs.min.js"></script>
<br/>
<!-- Just so that JSFiddle's Result label doesn't overlap the Chart -->
<div id="chartContainer" style="height: 360px; width: 100%;"></div>
<div>
  Angle :
  <input id="angle" type="text" placeholder="Enter Angle">
  <button id="addDataPoint">Add Data-Point</button>
</div>

JavaScript

var chart = new CanvasJS.Chart("chartContainer", {
    title: {
      text: "Adding Datapoint from user input"
    },
		axisY: {
    	minimum: 10
    },
    data: [{
      type: "line",
      dataPoints: [
      	{ x: 1, y: 10 }
      ]
    }]
});
chart.render();

function findY(x1,x2,angle){

	 return ((x2-x1) * Math.atan(angle*Math.PI/180))
}

//Function for add data-point
document.getElementById("addDataPoint").onclick = function() {
		var dps = chart.options.data[0].dataPoints;
    var angle = parseInt(document.getElementById("angle").value);
    var yValue = (findY(dps[dps.length-1].x, dps[dps.length-1].x + 1, angle) + dps[dps.length-1].y);
    if (yValue || yValue === 0) {
     	 chart.options.data[0].dataPoints.push({x: dps[dps.length-1].x + 1, y: yValue});
    	 chart.axisY[0].set("maximum", yValue);
    }

    chart.render();
}