[Chartjs]-How can I create a time series line graph in chart.js?

14👍

Basically, convert every single file-line string:

2020-02-15 18:37:39,-8.25 

into an Object:

{x: "2020-02-15 18:37:39", y: -8.25}

to be stored inside the Chart.js data : [] Array.

Here’s an example on how to create a function csvToChartData() that returns such an Array (to be used like: … data: csvToChartData(csv) )

  • Trim and split a file string by newline \n into a lines array .
  • Remove titles (the first array key) by using lines.shift();
  • Convert every line to an object {x: date, y: temperature} by splitting each line by comma .split(',')
  • Pass that newly mapped Array (by using .map()) as your chart data:
const csv = `Time,Temperature
2020-02-15 18:37:39,-8.25
2020-02-15 19:07:39,-8.08
2020-02-15 19:37:39,-8.41
2020-02-15 20:07:39,-8.2`;

const csvToChartData = csv => {
  const lines = csv.trim().split('\n');
  lines.shift(); // remove titles (first line)
  return lines.map(line => {
    const [date, temperature] = line.split(',');
    return {
      x: date,
      y: temperature
    }
  });
};

const ctx = document.querySelector("#line-chart").getContext('2d');
const config = {
  type: 'line',
  data: {
    labels: [],
    datasets: [{
      data: csvToChartData(csv),
      label: "Temperature",
      borderColor: "#3e95cd",
      fill: false
    }]
  },
  options: {
    scales: {
      xAxes: [{
        type: 'time',
        distribution: 'linear',
      }],
      title: {
        display: false,
      }
    }
  }
};
new Chart(ctx, config);
#line-chart {
  display: block;
  width: 100%;
}
<canvas id="line-chart"></canvas>
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.24.0/moment.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/chart.js@2.8.0"></script>

Fetch data dynamically:

enter image description here

To fetch the data dynamically, say every 5 seconds, you could use AJAX and the Fetch API.
Here’s the modified JS example given you have a CSV file called temperature.csv

const config = {
  type: "line",
  data: {
    labels: [],
    datasets: [{
      data: [], // Set initially to empty data
      label: "Temperature",
      borderColor: "#3e95cd",
      fill: false
    }]
  },
  options: {
    scales: {
      xAxes: [{
        type: "time",
        distribution: "linear"
      }],
      title: {
        display: false
      }
    }
  }
};

const ctx = document.querySelector("#line-chart").getContext("2d");
const temperatureChart = new Chart(ctx, config);

const csvToChartData = csv => {
  const lines = csv.trim().split("\n");
  lines.shift(); // remove titles (first line)
  return lines.map(line => {
    const [date, temperature] = line.split(",");
    return {
      x: date,
      y: temperature
    };
  });
};

const fetchCSV = () => fetch("temperature.csv")
  .then(data => data.text())
  .then(csv => {
    temperatureChart.data.datasets[0].data = csvToChartData(csv);
    temperatureChart.update();
    setTimeout(fetchCSV, 5000); // Repeat every 5 sec
  });

fetchCSV(); // First fetch!

Leave a comment