{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "description": "A bar graph showing the scores of the top 5 students. This shows an example of the window transform, for how the top K (5) can be filtered, and also how a rank can be computed for each student.",
  "background": "white",
  "padding": 5,
  "width": 200,
  "style": "cell",
  "data": [
    {
      "name": "source_0",
      "values": [
        {"student": "A", "score": 100},
        {"student": "B", "score": 56},
        {"student": "C", "score": 88},
        {"student": "D", "score": 65},
        {"student": "E", "score": 45},
        {"student": "F", "score": 23},
        {"student": "G", "score": 66},
        {"student": "H", "score": 67},
        {"student": "I", "score": 13},
        {"student": "J", "score": 12},
        {"student": "K", "score": 50},
        {"student": "L", "score": 79},
        {"student": "M", "score": 66},
        {"student": "N", "score": 30},
        {"student": "O", "score": 97},
        {"student": "P", "score": 75},
        {"student": "Q", "score": 24},
        {"student": "R", "score": 42},
        {"student": "S", "score": 76},
        {"student": "T", "score": 78},
        {"student": "U", "score": 21},
        {"student": "V", "score": 46}
      ]
    },
    {
      "name": "data_0",
      "source": "source_0",
      "transform": [
        {
          "type": "window",
          "params": [null],
          "as": ["rank"],
          "ops": ["rank"],
          "fields": [null],
          "sort": {"field": ["score"], "order": ["descending"]}
        },
        {"type": "filter", "expr": "datum.rank <= 5"}
      ]
    },
    {
      "name": "data_1",
      "source": "data_0",
      "transform": [
        {
          "type": "stack",
          "groupby": ["student"],
          "field": "score",
          "sort": {"field": [], "order": []},
          "as": ["score_start", "score_end"],
          "offset": "zero"
        },
        {
          "type": "filter",
          "expr": "isValid(datum[\"score\"]) && isFinite(+datum[\"score\"])"
        }
      ]
    }
  ],
  "signals": [
    {"name": "y_step", "value": 20},
    {
      "name": "height",
      "update": "bandspace(domain('y').length, 0.1, 0.05) * y_step"
    }
  ],
  "marks": [
    {
      "name": "marks",
      "type": "rect",
      "style": ["bar"],
      "from": {"data": "data_1"},
      "encode": {
        "update": {
          "fill": {"value": "#4c78a8"},
          "ariaRoleDescription": {"value": "bar"},
          "description": {
            "signal": "\"score: \" + (format(datum[\"score\"], \"\")) + \"; student: \" + (isValid(datum[\"student\"]) ? datum[\"student\"] : \"\"+datum[\"student\"])"
          },
          "x": {"scale": "x", "field": "score_end"},
          "x2": {"scale": "x", "field": "score_start"},
          "y": {"scale": "y", "field": "student"},
          "height": {"scale": "y", "band": 1}
        }
      }
    }
  ],
  "scales": [
    {
      "name": "x",
      "type": "linear",
      "domain": {"data": "data_1", "fields": ["score_start", "score_end"]},
      "range": [0, {"signal": "width"}],
      "nice": true,
      "zero": true
    },
    {
      "name": "y",
      "type": "band",
      "domain": {
        "data": "data_0",
        "field": "student",
        "sort": {"op": "average", "field": "score", "order": "descending"}
      },
      "range": {"step": {"signal": "y_step"}},
      "paddingInner": 0.1,
      "paddingOuter": 0.05
    }
  ],
  "axes": [
    {
      "scale": "x",
      "orient": "bottom",
      "gridScale": "y",
      "grid": true,
      "tickCount": {"signal": "ceil(width/40)"},
      "domain": false,
      "labels": false,
      "aria": false,
      "maxExtent": 0,
      "minExtent": 0,
      "ticks": false,
      "zindex": 0
    },
    {
      "scale": "x",
      "orient": "bottom",
      "grid": false,
      "title": "score",
      "labelFlush": true,
      "labelOverlap": true,
      "tickCount": {"signal": "ceil(width/40)"},
      "zindex": 0
    },
    {
      "scale": "y",
      "orient": "left",
      "grid": false,
      "title": "student",
      "zindex": 0
    }
  ]
}