Falkensee Population Example

{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "description": "An annotated line chart of the population of Falkensee, Germany.",
  "width": 500,
  "height": 250,
  "padding": 5,
  "config": {
    "title": {
      "fontSize": 16
    }
  },

  "title": {
    "text": {"signal": "'Population of Falkensee from ' + years[0] + ' to ' + years[1]"}
  },

  "data": [
    {
      "name": "table",
      "values": [
        {"year": 1875, "population": 1309},
        {"year": 1890, "population": 1558},
        {"year": 1910, "population": 4512},
        {"year": 1925, "population": 8180},
        {"year": 1933, "population": 15915},
        {"year": 1939, "population": 24824},
        {"year": 1946, "population": 28275},
        {"year": 1950, "population": 29189},
        {"year": 1964, "population": 29881},
        {"year": 1971, "population": 26007},
        {"year": 1981, "population": 24029},
        {"year": 1985, "population": 23340},
        {"year": 1989, "population": 22307},
        {"year": 1990, "population": 22087},
        {"year": 1991, "population": 22139},
        {"year": 1992, "population": 22105},
        {"year": 1993, "population": 22242},
        {"year": 1994, "population": 22801},
        {"year": 1995, "population": 24273},
        {"year": 1996, "population": 25640},
        {"year": 1997, "population": 27393},
        {"year": 1998, "population": 29505},
        {"year": 1999, "population": 32124},
        {"year": 2000, "population": 33791},
        {"year": 2001, "population": 35297},
        {"year": 2002, "population": 36179},
        {"year": 2003, "population": 36829},
        {"year": 2004, "population": 37493},
        {"year": 2005, "population": 38376},
        {"year": 2006, "population": 39008},
        {"year": 2007, "population": 39366},
        {"year": 2008, "population": 39821},
        {"year": 2009, "population": 40179},
        {"year": 2010, "population": 40511},
        {"year": 2011, "population": 40465},
        {"year": 2012, "population": 40905},
        {"year": 2013, "population": 41258},
        {"year": 2014, "population": 41777}
      ],
      "transform": [
        {
          "type": "extent",
          "field": "year",
          "signal": "years"
        }
      ]
    },
    {
      "name": "annotation",
      "values": [
        {
          "start": 1933,
          "end": 1945,
          "text": "Nazi Rule"
        },
        {
          "start": 1948,
          "end": 1989,
          "text": "GDR (East Germany)"
        }
      ]
    }
  ],

  "scales": [
    {
      "name": "x",
      "type": "linear",
      "range": "width",
      "zero": false,
      "domain": {"data": "table", "field": "year"}
    },
    {
      "name": "y",
      "type": "linear",
      "range": "height",
      "nice": true,
      "zero": true,
      "domain": {"data": "table", "field": "population"}
    },
    {
      "name": "color",
      "type": "ordinal",
      "domain": {"data": "annotation", "field": "text"},
      "range": ["black", "red"]
    }
  ],

  "axes": [
    {
      "orient": "left",
      "scale": "y",
      "title": "Population",
      "titlePadding": 10,
      "grid": true
    },
    {
      "orient": "bottom",
      "scale": "x",
      "format": "d",
      "title": "Year",
      "tickCount": 15
    }
  ],

  "marks": [
    {
      "type": "rect",
      "from": {"data": "annotation"},
      "encode": {
        "enter": {
          "x": {"scale": "x", "field": "start"},
          "x2": {"scale": "x", "field": "end"},
          "y": {"value": 0},
          "y2": {"signal": "height"},
          "fill": {"scale": "color", "field": "text"},
          "opacity": {"value": 0.2}
        }
      }
    },
    {
      "type": "line",
      "from": {"data": "table"},
      "encode": {
        "enter": {
          "interpolate": {"value": "monotone"},
          "x": {"scale": "x", "field": "year"},
          "y": {"scale": "y", "field": "population"},
          "stroke": {"value": "steelblue"},
          "strokeWidth": {"value": 3}
        }
      }
    },
    {
      "type": "symbol",
      "from": {"data": "table"},
      "encode": {
        "enter": {
          "x": {"scale": "x", "field": "year"},
          "y": {"scale": "y", "field": "population"},
          "stroke": {"value": "steelblue"},
          "strokeWidth": {"value": 1.5},
          "fill": {"value": "white"},
          "size": {"value": 30}
        }
      }
    }
  ],

  "legends": [
    {
      "fill": "color",
      "title": "Period",
      "orient": "top-left",
      "offset": 8,
      "encode": {
        "symbols": {
          "update": {
            "strokeWidth": {"value": 0},
            "shape": {"value": "square"},
            "opacity": {"value": 0.3}
          }
        }
      }
    }
  ]
}