Transforms allow for modifying the data before it is displayed on screen. They may filter or derive data, adding or removing fields or rows.

TODO: More about the data flow etc...


The following example uses the filter transform to retain only the rows that match the predicate expression.

  "data": { ... },
  "transform": [
      "type": "filter",
      "expr": "datum.end - datum.start < 5000"