Vega：在数据中添加缺失的信息

Question

在 kibana 中，在 Vega-lite 可视化中，我想随时间创建应用程序 (AAAA) 的转换状态图。 ( 时间线 )
状态有固定值 ( init , start , running ... )

在 x 轴上是时间戳，
在州一级，
用于跟踪状态级别的矩形或条形。

|====
| ======
| =============
_____________________________
t0      t1      t2 ....

我的数据来自 ElasticSearch 中的查询，格式如下。

timestamp  app  state
  t0    AAAA  Init
  t1    AAAA  start
  t2    AAAA  Running
  t3    AAAA  stopped

在 vega 中，我想用条形或矩形来表示状态， 例如：初始化状态将由一个从 t0 开始到 t1 结束的矩形表示。但我没有这个信息！ t1 在下一个数据行

是否可以通过利用下一行来计算这个值。 数据会是这样。

timestamp  app  state    ends 
  t0    AAAA  Init         t1
  t1    AAAA  start        t2 
  t2    AAAA  Running      t3
  t3    AAAA  stopped      t4 

欢迎任何帮助。

Answer 1

您可以使用lead 操作通过窗口变换来执行此操作，以找到下一个值。例如：

{
  "data": {
    "values": [
      {"timestamp": 0, "app": "A", "state": "init"},
      {"timestamp": 10, "app": "A", "state": "start"},
      {"timestamp": 25, "app": "A", "state": "run"},
      {"timestamp": 30, "app": "A", "state": "stop"},
      {"timestamp": 40, "app": "B", "state": "init"},
      {"timestamp": 55, "app": "B", "state": "start"},
      {"timestamp": 75, "app": "B", "state": "run"},
      {"timestamp": 85, "app": "B", "state": "stop"},
      {"timestamp": 90, "app": null, "state": "init"}
    ]
  },
  "transform": [
    {"window": [{"op": "lead", "field": "timestamp", "as": "t_stop"}]},
    {"filter": "datum.app != null"}
  ],
  "encoding": {
    "color": {"type": "nominal", "field": "app"},
    "x": {"type": "quantitative", "field": "timestamp"},
    "x2": {"type": "quantitative", "field": "t_stop"},
    "y": {
      "type": "nominal",
      "field": "state",
      "sort": {"op": "sum", "field": "timestamp", "order": "ascending"}
    }
  },
  "mark": "bar",
  "$schema": "https://vega.github.io/schema/vega-lite/v2.6.0.json"
}