Enumerator

Enumerator

let geminiSpec = {
  ...
  "enumerators": [
    {
      "name": "enumeratorName",
      "filter": "the_name_of_the_filter",
      "stepSize": stepSize,
      // or
      "values": [ ... ]
    },
    ...
  ]
}

Users can specify the enumerator for the steps so that the steps visit multiple states(/stops) of the chart enumerated by replacing the referred filter's value. For example, when interpolating a scatter plot of data from 1990 to 2019, an enumerator can make it visit every intermediate year.

Property	Type	Description
name	String	The identifier to be referred from the interpolate steps.
filter	String	The name of the Vega's filter object that is included in both start and end visualization specs. It will enumerate the literal value in the right hand side of the filter.expr.
stepSize	Number	When the filter's value is numeric, it enumerates the value with this step.
values	Array	Enumerating values for the filter it should include the start and end values.

There are two ways to apply enumerator. Here are examples.

Enumerator in a Step

let spec = {
  "timeline": [
    {
      "component": {"mark": "marks"},
      "timing": {"duration": 1000},
      "enumerator": "alongYears"
    }
  ],
  "enumerators": [ {"name": "alongYears", "filter": "year", "stepSize": 1} ]
}

Enumerator can be referred in a single step. In this case, it enumerates the data changes and interpolate with the timing info of the step.

Enumerator in a Concat Block

let spec = {
  "timeline": [
    {
      "concat": [
        {
          "component": {"mark": "marks"},
          "change": {"scale": false}, // change the data only
          "timing": {"duration": 1000}
        },
        {
          "component": {"mark": "marks"},
          "change": {"data": false}, // change the scale only
          "timing": {"duration": 1000}
        }
      ],
      "enumerator": "alongYears"
    }
  ],
  "enumerators": [ {"name": "alongYears", "filter": "year", "stepSize": 1} ]
}

Enumerator can be referred in a concat block. In this case, it enumerates the steps of the concat to show each data change and concatenates the set of the steps. Each enumerated step follows the timing of the original steps but with divding the durations and delays by the number of the enumeration so that they occupy the same duration.