Scatter Plot with multiple Y values for each X using VEGA

Elastic Stack Kibana
1

Hi I have a question visualizing multiple y values for each x in vega.
In case of simple x,y data like this (one data per one timestamp)

timestamp tag_value
2019-10-24 10:00:00 10.9
2019-10-24 10:0:01 11.0

I could easily draw the scatter plot using this vega script,

{
  $schema: https://vega.github.io/schema/vega-lite/v2.json
  data: {
    # URL object is a context-aware query to Elasticsearch
    url: {
      # The %-enclosed keys are handled by Kibana to modify the query
      # before it gets sent to Elasticsearch. Context is the search
      # filter as shown above the dashboard. Timefield uses the value 
      # of the time picker from the upper right corner.
      %context%: true
      %timefield%: @timestamp
      index: vega_test_data
      body: {
        size: 10000
        _source: ["@timestamp", "TAG_VALUE"]
      }
    }
    # We only need the content of hits.hits array
    format: {property: "hits.hits"}
  }
  transform: [
    {calculate: "toDate(datum._source['@timestamp'])", as: "time"}
  ]
  mark: point
  encoding: {
    x: {field: "time"
        type: "temporal"
        axis: {title: "Timestamp"}
        }
    y: {field: "_source.TAG_VALUE"
        type: "quantitative"
        axis : {title : "Tag Value"}
        }
  }
}

But, my y axis data has multiple values, so it is array type by each timestmap(x value)
For example,

timestamp tag_value
2019-10-24 10:00:00 [10.9, 11.0, 10.4 .....10.2]
2019-10-24 10:0:01 [10.7, 11.1, 10.5 .....12.2]

How can I draw multiple y values per x using vega?(The y values are array types per each x)

2

You need to flatten your data, e.g. convert

timestamp tag_value
2019-10-24 10:00:00 [10.9, 11.0, 10.4 .....10.2]
2019-10-24 10:0:01 [10.7, 11.1, 10.5 .....12.2]

to a flat table

timestamp tag_value
2019-10-24 10:00:00 10.9
2019-10-24 10:00:00 11.0
2019-10-24 10:00:00 10.4
... ...
2019-10-24 10:00:00 10.2
2019-10-24 10:0:01 10.7
2019-10-24 10:0:01 11.1
... ...

I saw that Vega-Lite has flatten transform, but I don't know which version added that, and if Kibana actually supports it. If it doesn't, you may have to switch to Vega and use flatten transform there (Kibana does support it).

3

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