Vega堆叠柱状图如何在柱顶添加总计标签？

要实现堆叠柱顶的总计标签，你只需在原有代码基础上新增2部分配置：聚合每个班次总工件数的数据集、用于显示总计值的文本标记，具体修改如下：

1. 新增总计聚合数据集 #

在data数组中追加以下配置，用于统计每个班次（smena）的总工件数：

{
  "name": "total",
  "source": "table",
  "transform": [
    {
      "type": "aggregate",
      "groupby": ["smena"],
      "fields": ["rozdilKusu"],
      "ops": ["sum"],
      "as": ["totalKusu"]
    }
  ]
}

2. 新增柱顶文本标记 #

在marks数组中追加以下配置，将总数值渲染到对应柱子的顶部：

{
  "type": "text",
  "from": {"data": "total"},
  "encode": {
    "enter": {
      "x": {"scale": "xscale", "field": "smena", "band": 0.5},
      "y": {"scale": "y", "field": "totalKusu", "offset": -5},
      "text": {"field": "totalKusu"},
      "align": {"value": "center"},
      "fill": {"value": "#000"},
      "fontSize": {"value": 12}
    }
  }
}

可选优化 #

如果总计标签被画布顶部截断，可以在y轴的scale配置中添加"padding": 15，给y轴顶部预留更多空间：

{
  "name": "y",
  "type": "linear",
  "range": "height",
  "nice": true, 
  "zero": true,
  "padding": 15,
  "domain": {"data": "table", "field": "y1"}
}

完整修改后代码 #

{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "description": "A basic stacked bar chart example.",
  "width": 500,
  "height": 200,
  "padding": 5,

  "data": [
    {
      "name": "table",
      "values": [
        {"smena": 0, "rozdilKusu": 28, "pocitadlo": 0}, {"smena": 0, "rozdilKusu": 55, "pocitadlo": 1},
        {"smena": 1, "rozdilKusu": 43, "pocitadlo": 0}, {"smena": 1, "rozdilKusu": 91, "pocitadlo": 1},
        {"smena": 2, "rozdilKusu": 25, "pocitadlo": 0}, {"smena": 2, "rozdilKusu": 53, "pocitadlo": 1},
        {"smena": 3, "rozdilKusu": 19, "pocitadlo": 0}, {"smena": 3, "rozdilKusu": 87, "pocitadlo": 1},
        {"smena": 4, "rozdilKusu": 52, "pocitadlo": 0}, {"smena": 4, "rozdilKusu": 48, "pocitadlo": 1},
        {"smena": 5, "rozdilKusu": 24, "pocitadlo": 0}, {"smena": 5, "rozdilKusu": 49, "pocitadlo": 1},
        {"smena": 6, "rozdilKusu": 87, "pocitadlo": 0}, {"smena": 6, "rozdilKusu": 66, "pocitadlo": 1},
        {"smena": 7, "rozdilKusu": 17, "pocitadlo": 0}, {"smena": 7, "rozdilKusu": 27, "pocitadlo": 1},
        {"smena": 8, "rozdilKusu": 68, "pocitadlo": 0}, {"smena": 8, "rozdilKusu": 16, "pocitadlo": 1},
        {"smena": 9, "rozdilKusu": 49, "pocitadlo": 0}, {"smena": 9, "rozdilKusu": 15, "pocitadlo": 1}
      ],
      "transform": [
        {
          "type": "stack",
          "groupby": ["smena"],
          "sort": {"field": "pocitadlo"},
          "field": "rozdilKusu"
        }
      ]
    },
    {
      "name": "total",
      "source": "table",
      "transform": [
        {
          "type": "aggregate",
          "groupby": ["smena"],
          "fields": ["rozdilKusu"],
          "ops": ["sum"],
          "as": ["totalKusu"]
        }
      ]
    }
  ],

  "scales": [
    {
      "name": "xscale",
      "type": "band",
      "range": "width",
      "domain": {"data": "table", "field": "smena"}
    },
    {
      "name": "y",
      "type": "linear",
      "range": "height",
      "nice": true, "zero": true,
      "padding": 15,
      "domain": {"data": "table", "field": "y1"}
    },
    {
      "name": "color",
      "type": "ordinal",
      "range": "category",
      "domain": {"data": "table", "field": "pocitadlo"}
    }
  ],

  "axes": [
    {"orient": "bottom", "scale": "xscale", "zindex": 1},
    {"orient": "left", "scale": "y", "zindex": 1}
  ],

  "marks": [
    {
      "type": "rect",
      "from": {"data": "table"},
      "encode": {
        "enter": {
          "x": {"scale": "xscale", "field": "smena"},
          "width": {"scale": "xscale", "band": 1, "offset": -1},
          "y": {"scale": "y", "field": "y0"},
          "y2": {"scale": "y", "field": "y1"},
          "fill": {"scale": "color", "field": "pocitadlo"},
          "tooltip": [{"field": "rozdilKusu", "type": "ordinal"}]
  
        },
        
        "update": {
          "fillOpacity": {"value": 1}
        },
        "hover": {
          "fillOpacity": {"value": 0.5}
        }
      }
    },
    {
      "type": "text",
      "from": {"data": "total"},
      "encode": {
        "enter": {
          "x": {"scale": "xscale", "field": "smena", "band": 0.5},
          "y": {"scale": "y", "field": "totalKusu", "offset": -5},
          "text": {"field": "totalKusu"},
          "align": {"value": "center"},
          "fill": {"value": "#000"},
          "fontSize": {"value": 12}
        }
      }
    }
  ]
}

内容的提问来源于stack exchange，提问作者Mirek Havelka