如何为多线图数据定义json

Question

我一直在尝试找出如何在 vega-lite 中定义多线图的数据，但我无法让它工作。这些示例在 URL 端点 ( https://vega.github.io/vega-editor/?mode=vega-lite&spec=line_color&showEditor=1 ) 显示 csv 文件的数据，但我想查看我在简单 json.

中定义的数据

这是我的单线图：

var LineSpec = {
  "description": "variation over time for",

  "data": {
     "values": 
     [
          {"date": "2012-04-23T18:25:43.511Z","price": 10},
          {"date": "2012-04-25T18:25:43.511Z","price": 7},
          {"date": "2012-04-27T18:25:43.511Z","price": 4},
          {"date": "2012-05-01T18:25:43.511Z","price": 1},
          {"date": "2012-05-03T18:25:43.511Z","price": 2},
          {"date": "2012-05-05T18:25:43.511Z","price": 6},
          {"date": "2012-05-07T18:25:43.511Z","price": 8},
          {"date": "2012-05-09T18:25:43.511Z","price": 4},
          {"date": "2012-05-11T18:25:43.511Z","price": 7}
      ]
    },
  "mark": "line",
  "encoding": {
    "x": {"field": "date", "type": "temporal"},
    "y": {"field": "price", "type": "quantitative"},
    "color": {"field": "symbol", "type": "nominal"}
  }
};

如何修改 "data" 以显示多线图？（如果可能的话，显示符号 table 中未定义的更多有用信息）。这是我现在看到的： Line graph with undefined symbol

谢谢！

Answer 1

您必须将符号字段添加到您的数据中。我添加了符号字段和符号 A 和 B。此数据应呈现图例中包含两个符号的多线图：

{
  "description": "variation over time for",
  "data": {
    "values": [
      {"date": "2012-04-23T18:25:43.511Z","price": 10, "symbol": "A"},
      {"date": "2012-04-25T18:25:43.511Z","price": 7, "symbol": "B"},
      {"date": "2012-04-27T18:25:43.511Z","price": 4, "symbol": "A"},
      {"date": "2012-05-01T18:25:43.511Z","price": 1, "symbol": "B"},
      {"date": "2012-05-03T18:25:43.511Z","price": 2, "symbol": "A"},
      {"date": "2012-05-05T18:25:43.511Z","price": 6, "symbol": "B"},
      {"date": "2012-05-07T18:25:43.511Z","price": 8, "symbol": "A"},
      {"date": "2012-05-09T18:25:43.511Z","price": 4, "symbol": "B"},
      {"date": "2012-05-11T18:25:43.511Z","price": 7, "symbol": "A"}
    ]
  },
  "mark": "line",
  "encoding": {
    "x": {"field": "date", "type": "temporal"},
    "y": {"field": "price", "type": "quantitative"},
    "color": {"field": "symbol", "type": "nominal"}
  }
}

如何为多线图数据定义json

how to define json for multi-line graph data

json

vega

vega-lite