      "signals": [
        {
          "name": "layout", "value": "squarify",
          "bind": {
            "input": "select",
            "options": [
              "squarify",
              "binary",
              "slicedice"
            ]
          }
        },
        {
          "name": "aspectRatio", "value": 1.6,
          "bind": { "input": "range", "min": 1, "max": 5, "step": 0.1 }
        }
      ],

      "data": [
        {
          "name": "tree",
          "url": "https://vega.github.io/edi