Is it possible to produce circular (round) shaped radar chart in Chart.js?

Question

When I plot a standard Chart.js radar chart, the axis is a polygon shape (not round). For example:

Is it possible to make the axis round shaped, like this?:

Answer 1

Edit [2021-10-27]: Chart.js v3 has removed scale option in favor of options.scales.r. Here's an updated way of making the radar grid circular.

const red = "rgb(255, 99, 132)";
const color = Chart.helpers.color;
const config = {
  type: 'radar',
  data: {
    labels: [['Eating', 'Dinner'], ['Drinking', 'Water'], 'Sleeping', ['Designing', 'Graphics'], 'Coding', 'Cycling', 'Running'],
    datasets: [{
      label: 'My dataset',
      backgroundColor: color(red).alpha(0.2).rgbString(),
      borderColor: red,
      pointBackgroundColor: red,
      data: [
        80,
        90,
        60,
        65,
        78,
        97,
        55
      ]
    }]
  },
  options: {
    scales: { // <-- Note change in options from scale to scales
        r: {
          grid: {
             circular: true
          },
          beginAtZero: true
        }
    }
  }
};

window.onload = function () {
  window.myRadar = new Chart(document.getElementById('chart'), config);
};

<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/3.6.0/chart.min.js"></script>
<canvas id="chart"></canvas>

Edit: Kudos to @timclutton for pointing to the axes styling section of the docs, which lists the circular property for the radar chart.

Original answer: After some digging it turned out that it is in fact possible. The trick is to add scale: { gridLines: { circular: true } } to options of the chart. Please see the snippet below. Note. As of 19 Jul 2019 I couldn't find this information in the official docs. So, it's either not documented yet or this feature might be changed / removed in future.

const red = "rgb(255, 99, 132)";
const color = Chart.helpers.color;
const config = {
  type: 'radar',
  data: {
    labels: [['Eating', 'Dinner'], ['Drinking', 'Water'], 'Sleeping', ['Designing', 'Graphics'], 'Coding', 'Cycling', 'Running'],
    datasets: [{
      label: 'My dataset',
      backgroundColor: color(red).alpha(0.2).rgbString(),
      borderColor: red,
      pointBackgroundColor: red,
      data: [
        80,
        90,
        60,
        65,
        78,
        97,
        55
      ]
    }]
  },
  options: {
    scale: {
      gridLines: {
        circular: true
      },
      ticks: {
        beginAtZero: true
      },
    }
  }
};

window.onload = function () {
  window.myRadar = new Chart(document.getElementById('chart'), config);
};

<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/Chart.min.js"></script>
<canvas id="chart"></canvas>

Answer 2

Since Version 3, the scale option has been deprecated. So to make the radar chart with circle gridlines, you have to pass the following option:

scales: {
  r: {
    grid: {
      circular: true,
    },
  },
},

const ctx = document.getElementById('radar-chart');

const data = {
  labels: [
    'Eating',
    'Drinking',
    'Sleeping',
    'Designing',
    'Coding',
    'Cycling',
    'Running'
  ],
  datasets: [{
    label: 'My First Dataset',
    data: [65, 59, 90, 81, 56, 55, 40],
    fill: true,
    backgroundColor: 'rgba(255, 99, 132, 0.2)',
    borderColor: 'rgb(255, 99, 132)',
    pointBackgroundColor: 'rgb(255, 99, 132)',
    pointBorderColor: '#fff',
    pointHoverBackgroundColor: '#fff',
    pointHoverBorderColor: 'rgb(255, 99, 132)'
  }, {
    label: 'My Second Dataset',
    data: [28, 48, 40, 19, 96, 27, 100],
    fill: true,
    backgroundColor: 'rgba(54, 162, 235, 0.2)',
    borderColor: 'rgb(54, 162, 235)',
    pointBackgroundColor: 'rgb(54, 162, 235)',
    pointBorderColor: '#fff',
    pointHoverBackgroundColor: '#fff',
    pointHoverBorderColor: 'rgb(54, 162, 235)'
  }]
};

const config = {
  type: 'radar',
  data: data,
  options: {
    scales: {
      r: {
        grid: {
          circular: true,
        },
      },
    },
    elements: {
      line: {
        borderWidth: 3
      }
    }
  },
};

const radarChart = new Chart(ctx, config);

<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/3.2.1/chart.min.js"></script>
<canvas id="radar-chart"></canvas>

Answer 3

You have to change line tension:

data:{
        labels: ['visionary', 'determination', 'extraversion', 'agreeableness', 'emotionality'],
        datasets: [{
          data: [
            34, 45, 67, 89, 22
          ],          
          label: 'me',
          lineTension: 0.5,
          borderColor: '#00ffff',
          backgroundColor: '#00ffff',
         
    }

Then your radar charts will be rounded just as you showed in the desired fashion

Answer 4

Perhaps not exactly what you are looking for; Chart.js documents a Polar area chart on it's samples page:

A quick example:

new Chart(document.getElementById("chart"), {
  type: "polarArea",
  data: {
    labels: ["a", "b", "c"],
    datasets: [{
      data: [10, 20, 30]
    }]
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.8.0/Chart.min.js"></script>
<canvas id="chart"></canvas>