Annual Temperature Example

A collection of small multiple area charts, showing average daily temperatures in Seattle for each hour of the day. For an alternative design using a colored heatmap, see the Heatmap example.

Vega JSON Specification <>

{
  "$schema": "https://vega.github.io/schema/vega/v3.0.json",
  "width": 800,
  "padding": 5,

  "config": {
    "title": {"fontSize": 14}
  },

  "title": {
    "text": "Seattle Annual Temperatures",
    "anchor": "start", "offset": 4
  },

  "signals": [
    {"name": "rangeStep", "value": 25},
    {"name": "height", "update": "rangeStep * 24"}
  ],

  "data": [
    {
      "name": "temperature",
      "url": "data/seattle-temps.csv",
      "format": {"type": "csv", "parse": {"temp": "number", "date": "date"}},
      "transform": [
        {"type": "formula", "as": "hour", "expr": "hours(datum.date)"},
        { "type": "formula", "as": "date",
          "expr": "datetime(year(datum.date), month(datum.date), date(datum.date))"}
      ]
    }
  ],

  "scales": [
    {
      "name": "row",
      "type": "band",
      "domain": [
        6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,
        0, 1, 2, 3, 4, 5
      ],
      "range": {"step": {"signal": "rangeStep"}}
    },
    {
      "name": "x",
      "type": "time",
      "domain": {"data": "temperature", "field": "date"},
      "range": "width"
    },
    {
      "name": "y",
      "type": "linear", "zero": false,
      "domain": {"data": "temperature", "field": "temp"},
      "range": [{"signal": "rangeStep"}, 1]
    }
  ],

  "axes": [
    {"orient": "bottom", "scale": "x", "domain": false, "title": "Month", "format": "%b"},
    {
      "orient": "left", "scale": "row", "domain": false, "title": "Hour",
      "tickSize": 0,
      "encode": {
        "labels": {
          "update": {
            "text": {"signal": "datum.value === 0 ? 'Midnight' : datum.value === 12 ? 'Noon' : datum.value < 12 ? datum.value + ':00 am' : (datum.value - 12) + ':00 pm'"}
          }
        }
      }
    }
  ],

  "marks": [
    {
      "type": "group",
      "from": {
        "facet": {
          "name": "hour",
          "data": "temperature",
          "groupby": "hour"
        }
      },
      "encode": {
        "enter": {
          "x": {"value": 0},
          "y": {"scale": "row", "field": "hour"},
          "width": {"signal": "width"},
          "height": {"signal": "rangeStep"}
        }
      },
      "marks": [
        {
          "type": "area",
          "from": {"data": "hour"},
          "encode": {
            "enter": {
              "x": {"scale": "x", "field": "date"},
              "y": {"scale": "y", "field": "temp"},
              "y2": {"signal": "rangeStep"}
            }
          }
        }
      ]
    }
  ]
}