{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "background": "white",
  "padding": 5,
  "title": {
    "text": "Barley Yield comparison between 1932 and 1931",
    "anchor": "start"
  },
  "data": [
    {
      "name": "source_0",
      "url": "data/barley.json",
      "format": {"type": "json"},
      "transform": [
        {
          "type": "pivot",
          "field": "year",
          "value": "yield",
          "groupby": ["variety", "site"]
        },
        {"type": "fold", "fields": ["1931", "1932"], "as": ["year", "yield"]},
        {"type": "formula", "expr": "toNumber(datum.year)", "as": "year"},
        {
          "type": "formula",
          "expr": "datum['1932'] - datum['1931']",
          "as": "delta"
        }
      ]
    },
    {
      "name": "column_domain",
      "source": "source_0",
      "transform": [{"type": "aggregate", "groupby": ["site"]}]
    }
  ],
  "signals": [
    {"name": "x_step", "value": 20},
    {
      "name": "child_width",
      "update": "bandspace(domain('x').length, 1, 0.5) * x_step"
    },
    {"name": "y_step", "value": 20},
    {
      "name": "child_height",
      "update": "bandspace(domain('y').length, 1, 0.5) * y_step"
    }
  ],
  "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": "Site", "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": "Variety",
          "zindex": 0
        }
      ]
    },
    {
      "name": "column_header",
      "type": "group",
      "role": "column-header",
      "from": {"data": "column_domain"},
      "sort": {"field": "datum[\"site\"]", "order": "ascending"},
      "title": {
        "text": {
          "signal": "isValid(parent[\"site\"]) ? parent[\"site\"] : \"\"+parent[\"site\"]"
        },
        "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[\"site\"]", "order": "ascending"},
      "encode": {"update": {"width": {"signal": "child_width"}}},
      "axes": [
        {
          "scale": "x",
          "orient": "bottom",
          "grid": false,
          "labelAlign": "right",
          "labelAngle": 270,
          "labelBaseline": "middle",
          "zindex": 0
        }
      ]
    },
    {
      "name": "cell",
      "type": "group",
      "style": "cell",
      "from": {
        "facet": {"name": "facet", "data": "source_0", "groupby": ["site"]}
      },
      "sort": {"field": ["datum[\"site\"]"], "order": ["ascending"]},
      "encode": {
        "update": {
          "width": {"signal": "child_width"},
          "height": {"signal": "child_height"},
          "stroke": {"value": null}
        }
      },
      "marks": [
        {
          "name": "child_pathgroup",
          "type": "group",
          "from": {
            "facet": {
              "name": "faceted_path_child_main",
              "data": "facet",
              "groupby": ["delta"]
            }
          },
          "encode": {
            "update": {
              "width": {"field": {"group": "width"}},
              "height": {"field": {"group": "height"}}
            }
          },
          "marks": [
            {
              "name": "child_marks",
              "type": "trail",
              "style": ["trail"],
              "sort": {"field": "datum[\"year\"]"},
              "from": {"data": "faceted_path_child_main"},
              "encode": {
                "update": {
                  "fill": {"scale": "color", "field": "delta"},
                  "tooltip": {
                    "signal": "{\"year\": format(datum[\"year\"], \"\"), \"yield\": isValid(datum[\"yield\"]) ? datum[\"yield\"] : \"\"+datum[\"yield\"]}"
                  },
                  "description": {
                    "signal": "\"year: \" + (isValid(datum[\"year\"]) ? datum[\"year\"] : \"\"+datum[\"year\"]) + \"; Variety: \" + (isValid(datum[\"variety\"]) ? datum[\"variety\"] : \"\"+datum[\"variety\"]) + \"; Yield Delta (%): \" + (format(datum[\"delta\"], \"\")) + \"; Barley Yield (bushels/acre): \" + (format(datum[\"yield\"], \"\")) + \"; yield: \" + (isValid(datum[\"yield\"]) ? datum[\"yield\"] : \"\"+datum[\"yield\"])"
                  },
                  "x": {"scale": "x", "field": "year"},
                  "y": {"scale": "y", "field": "variety"},
                  "size": {"scale": "size", "field": "yield"}
                }
              }
            }
          ]
        }
      ]
    }
  ],
  "scales": [
    {
      "name": "x",
      "type": "point",
      "domain": {"data": "source_0", "field": "year", "sort": true},
      "range": {"step": {"signal": "x_step"}},
      "padding": 0.5
    },
    {
      "name": "y",
      "type": "point",
      "domain": {"data": "source_0", "field": "variety", "sort": true},
      "range": {"step": {"signal": "y_step"}},
      "padding": 0.5
    },
    {
      "name": "color",
      "type": "linear",
      "domain": {"data": "source_0", "field": "delta"},
      "range": "diverging",
      "domainMid": 0,
      "interpolate": "hcl",
      "zero": false
    },
    {
      "name": "size",
      "type": "linear",
      "domain": {"data": "source_0", "field": "yield"},
      "range": [0, 12],
      "zero": true
    }
  ],
  "legends": [
    {
      "title": "Yield Delta (%)",
      "stroke": "color",
      "gradientLength": {"signal": "clamp(child_width, 100, 200)"}
    },
    {
      "title": "Barley Yield (bushels/acre)",
      "values": [20, 60],
      "strokeWidth": "size",
      "symbolType": "stroke"
    }
  ],
  "config": {"legend": {"orient": "bottom", "direction": "horizontal"}}
}