Draw a mathematical function in chartjs

Question

I'd like to know if it's possible to draw this function in chart js :

And have something that look like :

For now, using the solution given in an other post I have this result : But as you can see, the parabola part of the graph extends too far on the x-axis and therefore does not look like the expected result..

I'm using this code :

  const data = {
    labels: labels,
    datasets: [
      {
        function: function (x) {
          if (x <= Ec2) {
            return fck * (1 - Math.pow(1 - x / Ec2, n));
          } else {
            return fck;
          }
        },
        borderColor: 'red',
        data: [],
        fill: false,
        pointRadius: 0,
      },
    ],
  };

  Chart.pluginService.register({
    beforeInit: function (chart) {
      if (Ec2 > 0) {
        for (let i = 0; i <= Ec2; i += Ec2 / 5) {
          labels.push(i.toFixed(1));
        }
      }

      if (Ecu2 > 0) {
        labels.push(Ecu2);
      }

      var data = chart.config.data;

      for (var i = 0; i < data.datasets.length; i++) {
        for (var j = 0; j < data.labels.length; j++) {
          var fct = data.datasets[i].function,
            x = data.labels[j],
            y = fct(x);
          data.datasets[i].data.push(y);
        }
      }
    },
  });

user_1996066 · Answer

I think your code is just right, but there are not enough data points in the X axis and therefore the shape of the function looks like a totally different function.

Here is the same code with more X axis data points:

var Ec2 = 5
var fck = 2

var ctx = document.getElementById("myChart");
var data = {
  labels: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13],
  datasets: [{
    label: "f(x)",
    function: function(x) {
      if (x <= Ec2) {
        return fck * (1 - Math.pow(1 - x / Ec2, 2));
      } else {
        return fck;
      }
    },
    borderColor: "rgba(75, 192, 192, 1)",
    data: [],
    fill: false
  }]
};

Chart.pluginService.register({
  beforeInit: function(chart) {
    var data = chart.config.data;
    for (var i = 0; i < data.datasets.length; i++) {
      for (var j = 0; j < data.labels.length; j++) {
        var fct = data.datasets[i].function,
          x = data.labels[j],
          y = fct(x);
        data.datasets[i].data.push(y);
      }
    }
  }
});

var myBarChart = new Chart(ctx, {
  type: 'line',
  data: data,
  options: {
    title: {
      display: true
    },
    legend: {
      position: 'bottom'
    }
  }
});

I simply added more label entries with so that data.labels = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10].

Draw a mathematical function in chartjs

1 Answers