Framework:Javascript Data GridAngular Data GridReact Data GridVue Data Grid

React Charts: Markers

Data points in line, area and scatter series can be represented by markers.

Marker attributes such as shape, size, fill and stroke are configurable via the chart options:

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

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

Example: Marker Shape, Size and Colour

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

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 "./marker";

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.

Example: Custom Marker Shape

API Reference

Next Up

Continue to the next section to learn about formatters.