92
votes

I am trying to create a line chart with two datasets, each with its own Y scale / axis (one to the left, one to the right of the graph) using Chart.js.

This is my code (jsfiddle):

var canvas = document.getElementById('chart');
new Chart(canvas, {
  type: 'line',
  data: {
    labels: [ '1', '2', '3', '4', '5' ],
    datasets: [
      {
        label: 'A',
        yAxesGroup: 'A',
        data: [ 100, 96, 84, 76, 69 ]
      },
      {
        label: 'B',
        yAxesGroup: 'B',
        data: [ 1, 1, 1, 1, 0 ]
      }
    ]
  },
  options: {
    yAxes: [
      {
        name: 'A',
        type: 'linear',
        position: 'left',
        scalePositionLeft: true
      },
      {
        name: 'B',
        type: 'linear',
        position: 'right',
        scalePositionLeft: false,
        min: 0,
        max: 1
      }
    ]
  }
});

However, the second axis is not visible and the second dataset is still scaled exactly as the first (0 to 100 instead of 0 to 1). What do I need to change?

2

2 Answers

206
votes

For ChartJs 2.x only a couple changes need to be made (it looks like you have tried to combine 2.x options with the multi-axes options from my fork?),

  • The yAxes field needs to be in a scales object
  • the yAxis is referenced by id not name.
  • For the scale steps/size you just need to wrap these options in a ticks object.
  • No need forscalePositionLeft this is covered by position

Example:

var canvas = document.getElementById('chart');
new Chart(canvas, {
  type: 'line',
  data: {
    labels: ['1', '2', '3', '4', '5'],
    datasets: [{
      label: 'A',
      yAxisID: 'A',
      data: [100, 96, 84, 76, 69]
    }, {
      label: 'B',
      yAxisID: 'B',
      data: [1, 1, 1, 1, 0]
    }]
  },
  options: {
    scales: {
      yAxes: [{
        id: 'A',
        type: 'linear',
        position: 'left',
      }, {
        id: 'B',
        type: 'linear',
        position: 'right',
        ticks: {
          max: 1,
          min: 0
        }
      }]
    }
  }
});

fiddle example

0
votes

This solution is working in react.

// "chart.js": "^2.9.4"
// "react-chartjs-2": "^2.11.1"


const lineChartData = {
  data: {
    labels: ['1', '2', '3', '4', '5', '6'],
    datasets: [
      {
        label: '# of Votes',
        data: [12, 19, 3, 5, 2, 3],
        fill: false,
        backgroundColor: 'rgb(255, 99, 132)',
        borderColor: 'rgba(255, 99, 132, 0.2)',
      },
      {
        label: '# of Votes',
        data: [19, 9, 2, 1, 1, 21],
        fill: false,
        backgroundColor: 'rgb(122, 99, 255)',
        borderColor: 'rgba(102, 99, 255, 0.2)',
      }
    ],
  },
  options: {
    scales: {
      yAxes: [
        {
          type: 'linear',
          display: true,
          position: 'left',
          ticks: {
            beginAtZero: true,
          },
        },
        {
          type: 'linear',
          display: true,
          position: 'left',
          ticks: {
            beginAtZero: true,
          },
        },
      ],
    },
  }
}


<Line 
   data={lineChartData.data} 
   options={lineChartData.options} 
   height={30} 
   width={80} 
   options={{ maintainAspectRatio: true }} 
/>