{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "description": "The PM2.5 value of Beijing observed 15 days, highlighting the days when PM2.5 level is hazardous to human health. Data source https://chartaccent.github.io/chartaccent.html",
  "background": "white",
  "padding": 5,
  "height": 200,
  "style": "cell",
  "data": [
    {
      "name": "source_0",
      "values": [
        {"Day": 1, "Value": 54.8},
        {"Day": 2, "Value": 112.1},
        {"Day": 3, "Value": 63.6},
        {"Day": 4, "Value": 37.6},
        {"Day": 5, "Value": 79.7},
        {"Day": 6, "Value": 137.9},
        {"Day": 7, "Value": 120.1},
        {"Day": 8, "Value": 103.3},
        {"Day": 9, "Value": 394.8},
        {"Day": 10, "Value": 199.5},
        {"Day": 11, "Value": 72.3},
        {"Day": 12, "Value": 51.1},
        {"Day": 13, "Value": 112},
        {"Day": 14, "Value": 174.5},
        {"Day": 15, "Value": 130.5}
      ]
    },
    {"name": "source_1", "values": [{}]},
    {
      "name": "data_1",
      "source": "source_0",
      "transform": [
        {
          "type": "stack",
          "groupby": ["Day"],
          "field": "Value",
          "sort": {"field": [], "order": []},
          "as": ["Value_start", "Value_end"],
          "offset": "zero"
        },
        {
          "type": "filter",
          "expr": "isValid(datum[\"Value\"]) && isFinite(+datum[\"Value\"])"
        }
      ]
    },
    {
      "name": "data_2",
      "source": "source_0",
      "transform": [
        {"type": "filter", "expr": "datum.Value >= 300"},
        {"type": "formula", "expr": "300", "as": "baseline"},
        {
          "type": "filter",
          "expr": "isValid(datum[\"baseline\"]) && isFinite(+datum[\"baseline\"])"
        }
      ]
    }
  ],
  "signals": [
    {"name": "x_step", "value": 20},
    {
      "name": "width",
      "update": "bandspace(domain('x').length, 0.1, 0.05) * x_step"
    }
  ],
  "marks": [
    {
      "name": "layer_0_layer_0_marks",
      "type": "rect",
      "style": ["bar"],
      "from": {"data": "data_1"},
      "encode": {
        "update": {
          "fill": {"value": "#4c78a8"},
          "ariaRoleDescription": {"value": "bar"},
          "description": {
            "signal": "\"Day: \" + (isValid(datum[\"Day\"]) ? datum[\"Day\"] : \"\"+datum[\"Day\"]) + \"; Value: \" + (format(datum[\"Value\"], \"\"))"
          },
          "x": {"scale": "x", "field": "Day"},
          "width": {"scale": "x", "band": 1},
          "y": {"scale": "y", "field": "Value_end"},
          "y2": {"scale": "y", "field": "Value_start"}
        }
      }
    },
    {
      "name": "layer_0_layer_1_marks",
      "type": "rect",
      "style": ["bar"],
      "from": {"data": "data_2"},
      "encode": {
        "update": {
          "fill": {"value": "#e45755"},
          "ariaRoleDescription": {"value": "bar"},
          "description": {
            "signal": "\"Day: \" + (isValid(datum[\"Day\"]) ? datum[\"Day\"] : \"\"+datum[\"Day\"]) + \"; PM2.5 Value: \" + (format(datum[\"baseline\"], \"\")) + \"; Value: \" + (format(datum[\"Value\"], \"\"))"
          },
          "x": {"scale": "x", "field": "Day"},
          "width": {"scale": "x", "band": 1},
          "y": {"scale": "y", "field": "baseline"},
          "y2": {"scale": "y", "field": "Value"}
        }
      }
    },
    {
      "name": "layer_1_layer_0_marks",
      "type": "rule",
      "style": ["rule"],
      "from": {"data": "source_1"},
      "encode": {
        "update": {
          "stroke": {"value": "black"},
          "x": {"field": {"group": "width"}},
          "x2": {"value": 0},
          "y": {"scale": "y", "value": 300}
        }
      }
    },
    {
      "name": "layer_1_layer_1_marks",
      "type": "text",
      "style": ["text"],
      "from": {"data": "source_1"},
      "encode": {
        "update": {
          "align": {"value": "right"},
          "baseline": {"value": "bottom"},
          "text": {"value": "hazardous"},
          "dx": {"value": -2},
          "dy": {"value": -2},
          "fill": {"value": "black"},
          "x": {"field": {"group": "width"}},
          "y": {"scale": "y", "value": 300}
        }
      }
    }
  ],
  "scales": [
    {
      "name": "x",
      "type": "band",
      "domain": {
        "fields": [
          {"data": "data_1", "field": "Day"},
          {"data": "data_2", "field": "Day"}
        ],
        "sort": true
      },
      "range": {"step": {"signal": "x_step"}},
      "paddingInner": 0.1,
      "paddingOuter": 0.05
    },
    {
      "name": "y",
      "type": "linear",
      "domain": {
        "fields": [
          {"data": "data_1", "field": "Value_start"},
          {"data": "data_1", "field": "Value_end"},
          {"data": "data_2", "field": "baseline"},
          {"data": "data_2", "field": "Value"},
          [300]
        ]
      },
      "range": [{"signal": "height"}, 0],
      "nice": true,
      "zero": true
    }
  ],
  "axes": [
    {
      "scale": "y",
      "orient": "left",
      "gridScale": "x",
      "grid": true,
      "tickCount": {"signal": "ceil(height/40)"},
      "domain": false,
      "labels": false,
      "aria": false,
      "maxExtent": 0,
      "minExtent": 0,
      "ticks": false,
      "zindex": 0
    },
    {
      "scale": "x",
      "orient": "bottom",
      "grid": false,
      "title": "Day",
      "labelAngle": 0,
      "labelBaseline": "top",
      "zindex": 0
    },
    {
      "scale": "y",
      "orient": "left",
      "grid": false,
      "title": "PM2.5 Value",
      "labelOverlap": true,
      "tickCount": {"signal": "ceil(height/40)"},
      "zindex": 0
    }
  ]
}