Treemap Example

Treemaps display hierarchical data as a set of nested rectangles. This example shows the software class hierarchy of the Flare visualization toolkit (a precursor to D3 and Vega). Node areas are proportional to the file size in bytes of each source code file.

Vega JSON Specification <>

{
  "$schema": "https://vega.github.io/schema/vega/v3.0.json",
  "width": 960,
  "height": 500,
  "padding": 2.5,
  "autosize": "none",

  "signals": [
    {
      "name": "layout", "value": "squarify",
      "bind": {
        "input": "select",
        "options": [
          "squarify",
          "binary",
          "slicedice"
        ]
      }
    },
    {
      "name": "aspectRatio", "value": 1.6,
      "bind": {"input": "range", "min": 0.2, "max": 5, "step": 0.1}
    }
  ],

  "data": [
    {
      "name": "tree",
      "url": "data/flare.json",
      "transform": [
        {
          "type": "stratify",
          "key": "id",
          "parentKey": "parent"
        },
        {
          "type": "treemap",
          "field": "size",
          "sort": {"field": "value"},
          "round": true,
          "method": {"signal": "layout"},
          "ratio": {"signal": "aspectRatio"},
          "size": [{"signal": "width"}, {"signal": "height"}]
        }
      ]
    },
    {
      "name": "nodes",
      "source": "tree",
      "transform": [{ "type": "filter", "expr": "datum.children" }]
    },
    {
      "name": "leaves",
      "source": "tree",
      "transform": [{ "type": "filter", "expr": "!datum.children" }]
    }
  ],

  "scales": [
    {
      "name": "color",
      "type": "ordinal",
      "range": [
        "#3182bd", "#6baed6", "#9ecae1", "#c6dbef", "#e6550d",
        "#fd8d3c", "#fdae6b", "#fdd0a2", "#31a354", "#74c476",
        "#a1d99b", "#c7e9c0", "#756bb1", "#9e9ac8", "#bcbddc",
        "#dadaeb", "#636363", "#969696", "#bdbdbd", "#d9d9d9"
      ]
    },
    {
      "name": "size",
      "type": "ordinal",
      "domain": [0, 1, 2, 3],
      "range": [256, 28, 20, 14]
    },
    {
      "name": "opacity",
      "type": "ordinal",
      "domain": [0, 1, 2, 3],
      "range": [0.15, 0.5, 0.8, 1.0]
    }
  ],

  "marks": [
    {
      "type": "rect",
      "from": {"data": "nodes"},
      "interactive": false,
      "encode": {
        "enter": {
          "fill": {"scale": "color", "field": "name"}
        },
        "update": {
          "x": {"field": "x0"},
          "y": {"field": "y0"},
          "x2": {"field": "x1"},
          "y2": {"field": "y1"}
        }
      }
    },
    {
      "type": "rect",
      "from": {"data": "leaves"},
      "encode": {
        "enter": {
          "stroke": {"value": "#fff"}
        },
        "update": {
          "x": {"field": "x0"},
          "y": {"field": "y0"},
          "x2": {"field": "x1"},
          "y2": {"field": "y1"},
          "fill": {"value": "transparent"}
        },
        "hover": {
          "fill": {"value": "red"}
        }
      }
    },
    {
      "type": "text",
      "from": {"data": "nodes"},
      "interactive": false,
      "encode": {
        "enter": {
          "font": {"value": "Helvetica Neue, Arial"},
          "align": {"value": "center"},
          "baseline": {"value": "middle"},
          "fill": {"value": "#000"},
          "text": {"field": "name"},
          "fontSize": {"scale": "size", "field": "depth"},
          "fillOpacity": {"scale": "opacity", "field": "depth"}
        },
        "update": {
          "x": {"signal": "0.5 * (datum.x0 + datum.x1)"},
          "y": {"signal": "0.5 * (datum.y0 + datum.y1)"}
        }
      }
    }
  ]
}