theta

Overview

Theta is a special polar coordinate system that combines the characteristics of Transpose and Polar coordinate systems. It maps data to angles on a fixed radius, commonly used for transforming column charts to pie charts/donut charts/sector charts.

Theta coordinate system is essentially a combination of Transpose and Polar coordinate systems:

First, exchange x/y axis through Transpose
Then, convert Cartesian coordinates to polar coordinates through Polar
Finally, achieve angle encoding of data on a fixed radius

Configuration

Property	Description	Type	Default
startAngle	Starting angle (in radians), controls the starting angle position of pie/donut charts	`number`	`-Math.PI / 2`
endAngle	Ending angle (in radians), controls the ending angle position of pie/donut charts	`number`	`(Math.PI * 3) / 2`
innerRadius	Inner radius (ratio 0-1), controls the inner circle radius size of donut charts. 0 represents solid pie chart, greater than 0 represents donut chart. Generally we keep this value smaller than outerRadius. If it exceeds, it can still be displayed but may affect label display	`number`	`0`
outerRadius	Outer radius (ratio 0-1), controls the outer circle radius size of pie/donut charts. 1 represents filling the entire drawing area. Values greater than 1 will exceed the container (excess parts will be clipped)	`number`	`1`

Examples

Basic Pie Chart

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

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

chart.options({
  type: 'interval',
  data: [
    { category: 'A', value: 40 },
    { category: 'B', value: 25 },
    { category: 'C', value: 20 },
    { category: 'D', value: 15 },
  ],
  encode: { y: 'value', color: 'category' },
  transform: [{ type: 'stackY' }],
  coordinate: { type: 'theta' },
  style: { stroke: 'white' },
  labels: [{ text: 'category', radius: 0.8 }],
});

chart.render();

Basic Donut Chart

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

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

chart.options({
  type: 'interval',
  data: [
    { category: 'A', value: 40 },
    { category: 'B', value: 25 },
    { category: 'C', value: 20 },
    { category: 'D', value: 15 },
  ],
  encode: { y: 'value', color: 'category' },
  transform: [{ type: 'stackY' }],
  coordinate: {
    type: 'theta',
    innerRadius: 0.5, // Set inner radius to create donut chart
  },
  style: { stroke: 'white' },
  labels: [
    { text: 'category', radius: 0.5 },
    { text: 'value', radius: 0.5, style: { dy: 12 } },
  ],
});

chart.render();

Custom Starting Angle

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

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

chart.options({
  type: 'interval',
  data: [
    { category: 'A', value: 40 },
    { category: 'B', value: 25 },
    { category: 'C', value: 20 },
    { category: 'D', value: 15 },
  ],
  encode: { y: 'value', color: 'category' },
  transform: [{ type: 'stackY' }],
  coordinate: {
    type: 'theta',
    startAngle: -Math.PI / 2, // Start from π radians
    endAngle: Math.PI * 3, // End at 3π radians
  },
  style: { stroke: 'white' },
  labels: [{ text: 'category', radius: 0.8 }],
});

chart.render();

Compositional API Usage

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

const data = [
  { item: 'Case One', count: 40, percent: 0.4 },
  { item: 'Case Two', count: 21, percent: 0.21 },
  { item: 'Case Three', count: 17, percent: 0.17 },
  { item: 'Case Four', count: 13, percent: 0.13 },
  { item: 'Case Five', count: 9, percent: 0.09 },
];

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

chart.options({
  type: 'interval',
  coordinate: { type: 'theta' },
  data: data,
  transform: [{ type: 'stackY' }],
  encode: { y: 'percent', color: 'item' },
  legend: {
    color: { position: 'bottom', layout: { justifyContent: 'center' } },
  },
  labels: [
    {
      position: 'outside',
      text: (data) => `${data.item}: ${data.percent * 100}%`,
    },
  ],
  tooltip: {
    items: [
      (data) => ({
        name: data.item,
        value: `${data.percent * 100}%`,
      }),
    ],
  },
});

chart.render();