How can I produce a multi dataset line chart with correct Date X axis? #11732

DrKlipper · 2024-04-04T15:18:58Z

DrKlipper
Apr 4, 2024

Hi !
I need to plot some X/Y Data in a chart. I have multiple series of data and this is my sample:

<!DOCTYPE html>
<html lang="de">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Chart.js Testseite</title>
    <!-- Füge Chart.js hinzu -->
    <script src="https://cdn.jsdelivr.net/npm/chart.js"></script>
	<script src="https://cdn.jsdelivr.net/npm/chartjs-adapter-date-fns/dist/chartjs-adapter-date-fns.bundle.min.js"></script>
</head>
<body>
    <!-- Hier wird der Chart gerendert -->
    <div style="width: 80%; margin: auto;">
        <canvas id="myChart"></canvas>
    </div>

    <script>
        // Beispieldaten als Paare von Zeit und Wert
        const data = [
            { x: "2024-04-04T16:16:29.380969", y: 10 },
            { x: "2024-04-04T16:17:29.380969", y: 20 },
            { x: "2024-04-04T16:18:29.380969", y: 40 },
            { x: "2024-04-04T16:19:29.380969", y: 30 }
        ];
		
		const data2 = [
            { x: "2024-04-04T16:16:10.380969", y: 20 },
            { x: "2024-04-04T16:17:45.380969", y: 30 },
            { x: "2024-04-04T16:19:29.380969", y: 50 },
            { x: "2024-04-04T16:20:44.380969", y: 70 }
        ];

        // Konvertiere die Zeitstempel in Date-Objekte und Werte in Zahlen
        data.forEach(item => {
            item.time = new Date(item.time);
            item.value = parseFloat(item.value); // Konvertiere Wert zu einer Zahl
        });

        // Chart-Daten erstellen
        const chartData = {
            datasets: [{
                label: 'Wert 1',
                data: data,
                fill: false, 
                borderColor: 'rgb(75, 192, 192)'
            }, {
                label: 'Wert 2', 
                data: data2, 
                fill: false, 
                borderColor: 'rgb(175, 192, 192)' 
            }]
        };

        // Chart-Optionen konfigurieren
		const options = {
		}

        // Chart erstellen
        const ctx = document.getElementById('myChart').getContext('2d');
        const myChart = new Chart(ctx, {
            type: 'line',
            data: chartData,
            options: options
        });
    </script>
</body>
</html>

When I run this demo I got this strange output:

Can anyone help me out and show me a correct plotting?
What I need is a automatic scaling of the X axis. It should use the Min / Max datetime values from the data.
Is this even possible?

Any help would be much appreciated !

Dominik

stockiNail · 2024-04-04T16:45:37Z

stockiNail
Apr 4, 2024

@DrKlipper the problem is related to the X scale. You are not setting the type and by default for a line chart is a category one (string based).
But AFAI have seen, you want to use the time, therefore it is enough you set the X scale with type :"time".

const options = {
  scales: {
    x: {
      type: "time"
    }
  }
};

See codepen: https://codepen.io/stockinail/pen/LYvQGOV

4 replies

DrKlipper Apr 4, 2024
Author

Ok and how can I format the X Axis?
The DateTime format is not really readable ... I would prefer something like hh:mm or mm:ss
Is that possible, too ?

stockiNail Apr 4, 2024

Yes, of course. See scale config to change format:

// Chart-Optionen konfigurieren
const options = {
  scales: {
    x: {
      type: "time",
      ticks: {
        callback(value) {
          return this.format(value, "hh:mm")
        }
      }
    }
  }
};

DrKlipper Apr 4, 2024
Author

U made my day!
Will try it later.
Thx so far

stockiNail Apr 4, 2024

UR welcome

Provide feedback

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