Overview

legendFilter is an interaction feature that allows users to filter data displayed in the chart by clicking legend items. The filtering functionality supports two types of legends:

• Categorical legend: for filtering discrete data
• Continuous legend: for filtering continuous data

Through legend filtering, users can dynamically control the data items displayed in the chart, enhancing data exploration and analysis capabilities.

import { Chart } from '@antv/g2';

const chart = new Chart({
  container: 'container',
});

chart
  .data(temperatures)
  .encode('x', 'month')
  .encode('y', 'temperature')
  .encode('color', 'city')
  .call((chart) => chart.line())
  .call((chart) => chart.point());

chart.interaction('legendFilter', true);

chart.render();

Usage

Legend filtering functionality is enabled by default when using legends.

({
  type: 'interval',
  legend: {
    color: {},
    size: {},
  },
});

You can also manually set whether to enable it in interaction:

({
  type: 'interval',
  legend: {
    color: {},
    size: {},
  },
  interaction: {
    legendFilter: true, // Enable legend filter interaction
  },
});

Configuration Level

Legend filter interaction can be configured at the View level:

chart.interaction('legendFilter', true);

Configuration Options

The current version of the LegendFilter plugin has no configurable parameters. When calling, only the type needs to be specified:

Complex Type Description

The LegendFilter plugin internally automatically determines whether it's a categorical legend or continuous legend based on the legend type, and handles them differently:

• Categorical legend (className = legend-category): Click behavior is bound to filtering, supporting multi-select, cancel, and reset.
• Continuous legend (className = legend-continuous): Binds valuechange event to listen for slider changes.

The plugin automatically identifies this information through data and structure information injected into legend elements, without requiring manual specification by users.

legend Component Configuration

For detailed documentation see Legend component

Events

Getting Data

• legend:filter - Triggered when user filters through legend
• legend:reset - Triggered when all legend items are selected (reset state)

chart.on('legend:filter', (e) => {
  const { nativeEvent, data } = e;
  if (!nativeEvent) return;
  console.log(data);
});

chart.on('legend:reset', (e) => {
  const { nativeEvent } = e;
  if (!nativeEvent) return;
  console.log('end');
});

Triggering Interaction

• legend:filter - Trigger legend filtering
• legend:reset - Reset filter state

chart.emit('legend:filter', {
  data: { channel: 'color', values: ['Sports', 'Strategy'] },
});

chart.emit('legend:reset', {});

Examples

Below shows a legendfilter interaction functionality for discrete data.

import { Chart } from '@antv/g2';

const chart = new Chart({
  container: 'container',
});

chart.options({
  type: 'line',
  autoFit: true,
  height: 300,
  data: {
    type: 'fetch',
    value: 'https://assets.antv.antgroup.com/g2/temperatures1.json',
  },
  encode: {
    x: (d) => new Date(d.date),
    y: 'value',
    color: 'condition',
  },
});

chart.render();