JavaScript ChartsSeries Markers

Data points can be represented by markers in many series types, including line, area, scatter, and bubble.

Marker attributes such as shape, size, fill and stroke are configurable within each series.

These options are identical across series types, but differ in their location. Series without lines, such as scatter and bubble have these options on the series level, otherwise they are contained within the marker property.

series: [
    // ...
    marker: {
        shape: 'square', // defaults to 'circle'
        size: 20,
        fill: 'red',
        stroke: 'maroon',
    },
]

Please see the API reference for the list of all available options.

Marker Shape, Size and Colour

Notice how the shape and colour of the legend markers automatically match the shape and colour of the markers used by the series, but the size of the markers in the legend remains the same.

The legend item marker can be modified within the Legend Options.

Custom Marker Shapes

It's possible to define custom marker shapes with relative ease. All you have to do is extend the Marker class and define a single method called updatePath, for example to draw a heart:

import { Marker } from 'ag-charts-community';

export class Heart extends Marker {
    toRadians(degrees) {
        return (degrees / 180) * Math.PI;
    }

    updatePath() {
        const { x, path, size, toRadians } = this;
        const r = size / 4;
        const y = this.y + r / 2;

        path.clear();
        path.cubicArc(x - r, y - r, r, r, 0, toRadians(130), toRadians(330), 0);
        path.cubicArc(x + r, y - r, r, r, 0, toRadians(220), toRadians(50), 0);
        path.lineTo(x, y + r);
        path.closePath();
    }
}

Inside the marker object, you have access to the size of the marker, the x and y coordinates of the data point and the path instance, which you can use to issue draw commands. If you are familiar with the standard Canvas API, you'll feel right at home here. The path API is very similar to that of CanvasRenderingContext2D.

All we do is render two partial circles with the cubicArc command and then two straight lines using the lineTo and closePath commands to get the shape of a heart.

Inside the marker config of a series we then use the marker's constructor function itself rather than using one of the predefined shape names:

marker: {
    shape: Heart,
    size: 16,
}

The final result is shown in the example below.

API Reference