{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "description": "Stock price mean per quarter broken down by years.",
  "background": "white",
  "padding": 5,
  "data": [
    {
      "name": "source_0",
      "url": "data/stocks.csv",
      "format": {"type": "csv", "parse": {"date": "date"}},
      "transform": [
        {
          "field": "date",
          "type": "timeunit",
          "units": ["year"],
          "as": ["year_date", "year_date_end"]
        },
        {
          "field": "date",
          "type": "timeunit",
          "units": ["quarter"],
          "as": ["quarter_date", "quarter_date_end"]
        },
        {
          "type": "aggregate",
          "groupby": ["quarter_date", "symbol", "year_date"],
          "ops": ["mean"],
          "fields": ["price"],
          "as": ["mean_price"]
        },
        {
          "type": "filter",
          "expr": "isValid(datum[\"mean_price\"]) && isFinite(+datum[\"mean_price\"])"
        }
      ]
    },
    {
      "name": "column_domain",
      "source": "source_0",
      "transform": [{"type": "aggregate", "groupby": ["year_date"]}]
    }
  ],
  "signals": [
    {"name": "x_step", "value": 20},
    {
      "name": "child_width",
      "update": "bandspace(domain('x').length, 1, 0.5) * x_step"
    },
    {"name": "child_height", "value": 200}
  ],
  "layout": {
    "padding": 20,
    "offset": {"columnTitle": 10},
    "columns": {"signal": "length(data('column_domain'))"},
    "bounds": "full",
    "align": "all"
  },
  "marks": [
    {
      "name": "column-title",
      "type": "group",
      "role": "column-title",
      "title": {"text": "date (year)", "style": "guide-title", "offset": 10}
    },
    {
      "name": "row_header",
      "type": "group",
      "role": "row-header",
      "encode": {"update": {"height": {"signal": "child_height"}}},
      "axes": [
        {
          "scale": "y",
          "orient": "left",
          "grid": false,
          "title": "Mean of price",
          "labelOverlap": true,
          "tickCount": {"signal": "ceil(child_height/40)"},
          "zindex": 0
        }
      ]
    },
    {
      "name": "column_header",
      "type": "group",
      "role": "column-header",
      "from": {"data": "column_domain"},
      "sort": {"field": "datum[\"year_date\"]", "order": "ascending"},
      "title": {
        "text": {
          "signal": "timeFormat(parent[\"year_date\"], timeUnitSpecifier([\"year\"], {\"year-month\":\"%b %Y \",\"year-month-date\":\"%b %d, %Y \"}))"
        },
        "style": "guide-label",
        "frame": "group",
        "offset": 10
      },
      "encode": {"update": {"width": {"signal": "child_width"}}}
    },
    {
      "name": "column_footer",
      "type": "group",
      "role": "column-footer",
      "from": {"data": "column_domain"},
      "sort": {"field": "datum[\"year_date\"]", "order": "ascending"},
      "encode": {"update": {"width": {"signal": "child_width"}}},
      "axes": [
        {
          "scale": "x",
          "orient": "bottom",
          "grid": false,
          "title": "date (quarter)",
          "format": {
            "signal": "timeUnitSpecifier([\"quarter\"], {\"year-month\":\"%b %Y \",\"year-month-date\":\"%b %d, %Y \"})"
          },
          "formatType": "time",
          "labelOverlap": true,
          "zindex": 0
        }
      ]
    },
    {
      "name": "cell",
      "type": "group",
      "style": "cell",
      "from": {
        "facet": {"name": "facet", "data": "source_0", "groupby": ["year_date"]}
      },
      "sort": {"field": ["datum[\"year_date\"]"], "order": ["ascending"]},
      "encode": {
        "update": {
          "width": {"signal": "child_width"},
          "height": {"signal": "child_height"}
        }
      },
      "marks": [
        {
          "name": "child_marks",
          "type": "symbol",
          "style": ["point"],
          "from": {"data": "facet"},
          "encode": {
            "update": {
              "fill": {"value": "transparent"},
              "stroke": {"scale": "color", "field": "symbol"},
              "ariaRoleDescription": {"value": "point"},
              "description": {
                "signal": "\"date (quarter): \" + (timeFormat(datum[\"quarter_date\"], timeUnitSpecifier([\"quarter\"], {\"year-month\":\"%b %Y \",\"year-month-date\":\"%b %d, %Y \"}))) + \"; Mean of price: \" + (format(datum[\"mean_price\"], \"\")) + \"; symbol: \" + (isValid(datum[\"symbol\"]) ? datum[\"symbol\"] : \"\"+datum[\"symbol\"])"
              },
              "x": {"scale": "x", "field": "quarter_date"},
              "y": {"scale": "y", "field": "mean_price"}
            }
          }
        }
      ],
      "axes": [
        {
          "scale": "y",
          "orient": "left",
          "gridScale": "x",
          "grid": true,
          "tickCount": {"signal": "ceil(child_height/40)"},
          "domain": false,
          "labels": false,
          "aria": false,
          "maxExtent": 0,
          "minExtent": 0,
          "ticks": false,
          "zindex": 0
        }
      ]
    }
  ],
  "scales": [
    {
      "name": "x",
      "type": "point",
      "domain": {"data": "source_0", "field": "quarter_date", "sort": true},
      "range": {"step": {"signal": "x_step"}},
      "padding": 0.5
    },
    {
      "name": "y",
      "type": "linear",
      "domain": {"data": "source_0", "field": "mean_price"},
      "range": [{"signal": "child_height"}, 0],
      "nice": true,
      "zero": true
    },
    {
      "name": "color",
      "type": "ordinal",
      "domain": {"data": "source_0", "field": "symbol", "sort": true},
      "range": "category"
    }
  ],
  "legends": [
    {
      "stroke": "color",
      "symbolType": "circle",
      "title": "symbol",
      "encode": {"symbols": {"update": {"fill": {"value": "transparent"}}}}
    }
  ]
}