Smaller scale for volume dataset in Chart JS

Question

I'm graphing some stocks data and I wanted to put the volume in a smaller gray bar dataset at the bottom, like in Yahoo Finance.

What I want:

The small grey dataset is at the bottom.

What I get:

Three different Y scales and the size of the volume dataset is the same a the other.

My code:

When I create the chart:

new Chart(context, {
    type: 'line',
    data: {
      labels: timestamps.map(n => 
        (new Date(n * 1000)).toLocaleString()
      ),
      datasets: [
        dataset,
        vdataset
      ]
    },
    options: {
      maintainAspectRatio: false,
      scales: {
        xAxis: {
          // type: 'time'
          ticks: {
            //autoSkip: true,
            maxTicksLimit: 10
          }
        },
        yAxes: [{
          id: 'volume',
          display: false
        }],
        y: {
          beginAtZero: false
        },
      },
      animation: {
        duration: 0
      },
      plugins: {
        autocolors: false,
        annotation: {
          annotations
        }
      },
      tooltips: {
        mode: 'nearest'
      },
      hover: {
        intersect: false
      }
    }
  });

The volume dataset:

{
    type: 'bar',
    label: `Volume`,
    data: ...,
    backgroundColor: 'transparent',
    borderColor: 'grey',
    fill: 'origin',
    pointRadius: 0,
    borderWidth: 2,
    yAxisID: 'volume'
  }

Answer 1

you need to give every dataset a yAxisID and then you should name your axis with that id like this:

Data:

var data = {
  labels: labels,
  datasets: [{
    label: 'My First Dataset',
    data: generateTestSeries(),
    fill: false,
    borderColor: 'rgb(75, 192, 192)',
    tension: 0.1,
    yAxisID: "something",
  },
  {
    label: 'My Second Dataset',
    data: generateTestSeries(),
    fill: false,
    borderColor: 'rgb(182, 50, 192)',
    tension: 0.1,
    yAxisID: "volume",
  },
  ]
};

Scales:

scales: {
    volume: {
        axis: "y",  
        min: -80,
        max: 60,
        position: 'right',
    },
    something: {
        axis: "y",
        min: -20,
        max: 70,
        position: 'left',
    }
}

Also you shouldn't have the list yAxes, that was how axes were defined in chartjs 2.x

Here is a fiddle to see this in use: JSFiddle

edit: If you want an invisible axis just set display to false as seen in the now updated Fiddle.