Vega Heatmap

heatmap.json

{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "description": "A heatmap showing average daily temperatures in Seattle for each hour of the day.",
  "width": 800,
  "height": 500,
  "padding": 5,

  "title": {
    "text": "Seattle Annual Temperatures",
    "anchor": "middle",
    "fontSize": 16,
    "offset": 4
  },

  "scales": [
    {
      "name": "x",
      "type": "time",
      "domain": {"data": "temperature", "field": "date"},
      "range": "width"
    },
    {
      "name": "y",
      "type": "band",
      "domain": {"data": "temperature", "field": "time"},
      "range": "height"
    },
    {
      "name": "color",
      "type": "linear",
      "range": {"scheme": "Viridis"},
      "domain": {"data": "temperature", "field": "temp"},
      "reverse": false,
      "zero": false, "nice": true
    }
  ],

  "axes": [
    {"orient": "bottom", "scale": "x", "domain": false, "title": "Month"},
    {
      "orient": "left", "scale": "y", "domain": false, "title": "Hour"
    }
  ],

  "legends": [
    {
      "fill": "color",
      "type": "gradient",
      "title": "Avg. Temp (°F)",
      "titleFontSize": 12,
      "titlePadding": 4,
      "gradientLength": {"signal": "height - 16"}
    }
  ],

  "marks": [
    {
      "type": "rect",
      "from": {"data": "temperature"},
      "encode": {
        "enter": {
          "x": {"scale": "x", "field": "date"},
          "y": {"scale": "y", "field": "time"},
          "width": {"value": 5},
          "height": {"scale": "y", "band": 1}
        },
        "update": {
          "fill": {"scale": "color", "field": "temp"}
        }
      }
    }
  ]
}