How do I create a heatmap chart in JavaScript?

Install with `npm install katucharts.js`, then call KatuCharts.chart(container, { chart: { type: 'heatmap' }, series: [...] }).

Why does my heatmap chart render as a line chart?

The chart type was not registered. KatuCharts logs "KatuCharts: unknown series type " ", falling back to line" and draws a line chart rather than throwing. Import the module the type belongs to — for example `import 'katucharts.js/bio';` — before creating the chart.

Why do I get "Cannot read properties of null (reading 'appendChild')"?

The container element does not exist when the chart is created. Create the chart after the element is in the DOM: in React that means inside useEffect, not during render.

Why is the chart rendering with zero height?

The container has no height. A div with no content collapses to zero. Give it a height in CSS, or pass `chart: { height: 400 }` in the options.

Other

Heatmap

type: 'heatmap'

Grid of colored rectangles with a sequential color scale. Requires colorAxis to map values to colors.

Edit the JSON on the right and press Run (or ⌘/Ctrl + Enter) — data, titles, categories and colors all update live.

Live

Heatmap

Edit · JSON

{
  "chart": {
    "type": "heatmap"
  },
  "title": {
    "text": "Performance Matrix"
  },
  "xAxis": {
    "categories": [
      "Speed",
      "Memory",
      "CPU",
      "Network",
      "Disk"
    ]
  },
  "series": [
    {
      "name": "Score",
      "data": [
        [
          0,
          0,
          85
        ],
        [
          1,
          0,
          72
        ],
        [
          2,
          0,
          90
        ],
        [
          3,
          0,
          65
        ],
        [
          4,
          0,
          78
        ],
        [
          0,
          1,
          60
        ],
        [
          1,
          1,
          88
        ],
        [
          2,
          1,
          55
        ],
        [
          3,
          1,
          92
        ],
        [
          4,
          1,
          70
        ],
        [
          0,
          2,
          95
        ],
        [
          1,
          2,
          43
        ],
        [
          2,
          2,
          78
        ],
        [
          3,
          2,
          80
        ],
        [
          4,
          2,
          62
        ],
        [
          0,
          3,
          50
        ],
        [
          1,
          3,
          67
        ],
        [
          2,
          3,
          82
        ],
        [
          3,
          3,
          45
        ],
        [
          4,
          3,
          91
        ],
        [
          0,
          4,
          73
        ],
        [
          1,
          4,
          81
        ],
        [
          2,
          4,
          60
        ],
        [
          3,
          4,
          76
        ],
        [
          4,
          4,
          55
        ]
      ]
    }
  ]
}

Data format

{ x: number, y: number, value: number }

Data shape

The JSON you pass inside the chart — drop it straight into your series.

data: [
  [0, 0, 85],
  [1, 0, 72],
  [2, 0, 90],
  [0, 1, 60],
  [1, 1, 88]
]

Example

import KatuCharts from 'katucharts.js';

KatuCharts.chart('container', {
  chart: { type: 'heatmap' },
  colorAxis: { min: 0, max: 100 },
  series: [{
    data: [
      [0, 0, 85], [1, 0, 72], [2, 0, 90],
      [0, 1, 60], [1, 1, 88]
    ]
  }]
});

Type-specific options

Option	Description
`colorAxis`	{ min, max, minColor, maxColor, stops, dataClasses }.
`colsize / rowsize`	Cell dimensions in data units.
`nullColor / interpolation`	Missing-value color / smooth interpolation.

Variations

Discrete color classes

Bucket values into named ranges with colorAxis.dataClasses instead of a continuous scale.

KatuCharts.chart('container', {
  chart: { type: 'heatmap' },
  colorAxis: {
    dataClasses: [
      { to: 50, color: '#7A8450', name: 'Low' },
      { from: 50, to: 75, color: '#C9762B', name: 'Mid' },
      { from: 75, color: '#B43417', name: 'High' }
    ]
  },
  series: [{
    dataLabels: { enabled: true, format: '{point.value}' },
    data: [[0,0,85],[1,0,72],[2,0,90]]
  }]
});

Common errors

Why does my heatmap chart render as a line chart?: The chart type was not registered. KatuCharts logs "KatuCharts: unknown series type "<type>", falling back to line" and draws a line chart rather than throwing. Import the module the type belongs to — for example `import 'katucharts.js/bio';` — before creating the chart.
Why do I get "Cannot read properties of null (reading 'appendChild')"?: The container element does not exist when the chart is created. Create the chart after the element is in the DOM: in React that means inside useEffect, not during render.
Why is the chart rendering with zero height?: The container has no height. A div with no content collapses to zero. Give it a height in CSS, or pass `chart: { height: 400 }` in the options.

FAQ

How do I create a heatmap chart in JavaScript?: Install with `npm install katucharts.js`, then call KatuCharts.chart(container, { chart: { type: 'heatmap' }, series: [...] }).
Why does my heatmap chart render as a line chart?: The chart type was not registered. KatuCharts logs "KatuCharts: unknown series type "<type>", falling back to line" and draws a line chart rather than throwing. Import the module the type belongs to — for example `import 'katucharts.js/bio';` — before creating the chart.
Why do I get "Cannot read properties of null (reading 'appendChild')"?: The container element does not exist when the chart is created. Create the chart after the element is in the DOM: in React that means inside useEffect, not during render.
Why is the chart rendering with zero height?: The container has no height. A div with no content collapses to zero. Give it a height in CSS, or pass `chart: { height: 400 }` in the options.

Common options (color, visible, marker, dataLabels, animation, events, zones…) apply to every type — see Configuration → series. See it rendered in the gallery.