title: Relative bar chart overlay on line chart in chart.js
body: <p>I'm trying to build a chart in chart.js, showing price data of a virtual item, with a line chart showing pricing, and a backlay bar chart, showing sales volume, like this:
  <a href="https://i.stack.imgur.com/YphHh.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/YphHh.png" alt="enter image description here"></a></p>
  
  <p>My issue is, the y-axis is the same for both, meaning the price data is shown at the bottom with unnoticeable differences, since the volume is in the hundreds. </p>
  
  <p>I want the price data to be on the y-axis, with the bars shown relatively, with the highest volume being shown as 100% height, not the values on the y-axis, something more like this:</p>
  
  <p><a href="https://i.stack.imgur.com/QLf17.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/QLf17.png" alt="enter image description here"></a></p>
  
  <p>Is this possible, and how would it be done? Thanks!</p>
  
  <p>Code:</p>
  
  <pre><code>let marketData = [["Nov 28 2018 20: +0",30.332,"103"],["Nov 28 2018 21: +0",25.801,"188"],["Nov 28 2018 22: +0",25.451,"262"],["Nov 28 2018 23: +0",12.484,"693"]];
  
  let lineData = [];
  let barData = [];
  let labels = [];
  
  marketData.forEach(function(thing) {
      labels.push(thing[0].replace(' +0', '00'));
      lineData.push(thing[1]);
      barData.push(thing[2]);
  });
  
  new Chart(document.getElementById("mixed-chart"), {
      type: 'bar',
      data: {
        labels: labels,
        datasets: [
          {
            label: "Price",
            type: "line",
            borderColor: "#3e95cd",
            data: lineData,
            fill: false
          },
          {
            label: "Sold",
            type: "bar",
            backgroundColor: "rgba(0,0,0,0.2)",
            data: barData
          }
        ]
      },
      options: {
        title: {
          display: true,
          text: 'Sale price vs sale volume'
        },
        legend: { display: false }
      }
  });
  </code></pre>