Pre-grouped data in JSON input?

[kevreth]

This data, intended for a grouped bar chart,

    Year,Rentals,VHS
    2002,184,84
    2003,180,67

transforms to JSON as

          {
            "Year": 2002,
            "Rentals": 184,
            "Sales": 84
          },
          {
            "Year": 2003,
            "Rentals": 180,
            "Sales": 67
          }

If that JSON data format compatible with vega-lite? All the examples I see have a format like

        [
            {"year":2002,"type":"Rentals","volume":"184"},
            {"year":2002,"type":"Sales","volume":"84"},
            {"year":2003,"type":"Rentals","volume":"180"},
            {"year":2003,"type":"Sales","volume":"67"}
        ]

[jakevdp]

This is what the Fold transform is used for. For example:

{
  "data": {
    "values": [
      {"Year": 2002, "Rentals": 184, "Sales": 84},
      {"Year": 2003, "Rentals": 180, "Sales": 67}
    ]
  },
  "transform": [{"fold": ["Rentals", "Sales"], "as": ["type", "value"]}],
  "mark": "bar",
  "encoding": {
    "x": {"field": "value", "type": "quantitative"},
    "y": {"field": "Year", "type": "ordinal"},
    "color": {"field": "type", "type": "nominal"}
  }
}

[kevreth]

Excellent, thank you.