ResolveFilter Transform

The resolvefilter transform uses the filter mask generated by a crossfilter transform to efficiently generate filtered data streams. A single crossfilter instance can be used to support cross-filtering over multiple charts; the filtered data streams for each individual chart are generated by using one resolvefilter transform per chart.

A resolvefilter transform should always be followed by a consuming transform, such as an aggregate. To simply collect the filtered data objects, add a collect transform after resolvefilter.

Transform Parameters

Property	Type	Description
filter	Signal	Required. A signal reference to a backing crossfilter transform.
ignore	Number	Required. A bit mask indicating which fields in the crossfilter should be ignored. Each bit corresponds to a field and query in the crossfilter transform’s fields and query arrays. If the corresponding bit is on, that field and query will be ignored when resolving the filter. All other queries must pass the filter for a tuple to be included down stream.

Usage

This example cross-filters the delay, time, and distance fields in a data set of flights. The crossfilter transform sets up the filters, using range queries defined by signal values. The three derived data sets use resolvefilter transforms to filter the data, in each case ignoring one of the fields. For example, the "filterTimeDistance" data set filters the data by the time and distance queries, ignoring the delay query.

{
  "signals": [
    { "name": "delayRange", "value": [-60, 180] },
    { "name": "timeRange", "value": [0, 24] },
    { "name": "distanceRange", "value": [0, 2400] },
  ],
  "data": [
    {
      "name": "flights",
      "url": "data/flights-200k.json",
      "transform": [
        {
          "type": "crossfilter",
          "signal": "xfilter",
          "fields": ["delay", "time", "distance"],
          "query": [
            {"signal": "delayRange"},
            {"signal": "timeRange"},
            {"signal": "distanceRange"}
          ]
        }
      ]
    },
    {
      "name": "filterTimeDistance",
      "source": "flights",
      "transform": [
        {
          "type": "resolvefilter",
          "filter": {"signal": "xfilter"},
          "ignore": 1,

        },
        ...
      ]
    },
    {
      "name": "filterDelayDistance",
      "source": "flights",
      "transform": [
        {
          "type": "resolvefilter",
          "filter": {"signal": "xfilter"},
          "ignore": 2
        },
        ...
      ]
    },
    {
      "name": "filterDelayTime",
      "source": "flights",
      "transform": [
        {
          "type": "resolvefilter",
          "filter": {"signal": "xfilter"},
          "ignore": 4
        },
        ...
      ]
    }
  ]
}