Markers

This section explores the markers used by line, area and scatter series.

The shape of the markers can be changed by using the shape config. The size, fill and stroke are also valid configs:

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

enabledWhether or not to show markers.
Default: true
shapeThe shape to use for the markers. You can also supply a custom marker by providing a Marker subclass.
Default: 'circle'
Options: 'circle' | 'cross' | 'diamond' | 'plus' | 'square' | 'triangle'
sizeThe size in pixels of the markers.
Default: 8
minSizeFor series where the size of the marker is determined by the data, this determines the smallest size a marker can be in pixels.
Default: 12
fillThe colour to use for marker fills. If this is not specified, the markers will take their fill from the series.
strokeThe colour to use for marker strokes. If this is not specified, the markers will take their stroke from the series.
strokeWidthThe width in pixels of the marker stroke. If this is not specified, the markers will take their stroke width from the series.
formatterFunction used to return formatting for individual markers, based on the supplied information. If the current marker is highlighted, the highlighted property will be set to true; make sure to check this if you want to differentiate between the highlighted and un-highlighted states.function(params: IParams): IReturn; interface IParams { datum: any; fill: string; stroke: string; strokeWidth: number; size: number; highlighted: boolean; xKey: string; yKey: string; } interface IReturn { fill: string; stroke: string; strokeWidth: number; size: number; }

Next Up

Continue to the next section to learn about tooltips.