drawing sine wave in canvas

Question

I am trying to draw a simple sine wave in a canvas but i am not getting it right. this is my desired output as in the picture.

What I have got so far is http://jsfid

Answer 1

Use bezierCurveTo, this is only an example you should adjust parameters to get nice sinusoid

var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.moveTo(50,50);
ctx.bezierCurveTo(120,-100,200,250,250,50);
ctx.bezierCurveTo(300,-100,350,250,430,50);
ctx.lineWidth = 5;
ctx.strokeStyle = '#003300';
ctx.stroke();

<canvas id="myCanvas" width="550" height="360" style="border:1px solid #d3d3d3;">

Answer 2

function plotSine(amplitude, frequency) {
  const canvas = document.getElementById('canvas');
  if (canvas.getContext) {
    const ctx = canvas.getContext('2d');
    
    ctx.clearRect(0, 0, canvas.width, canvas.height);
    
    ctx.beginPath();
    
    ctx.strokeStyle = '#343a40';
    ctx.lineWidth = 2;
    
    var x = 0;
    var y = 0;
    
    while (x < canvas.width) {
      y = (canvas.height / 2) + amplitude * Math.sin(x / frequency);
      ctx.lineTo(x, y);
      
      x += 1;
    }
    
    ctx.stroke();
  }
}

plotSine(40, 20);

code {
  background-color: #eee;
  border-radius: 3px;
  padding: 0 3px;
}

<canvas id="canvas" width="480" height="360">
  <p>
    Your browser does not support the <code>&lt;canvas&gt;</code> element.
  </p>
</canvas>