viewof chart = vega({
"$schema": "https://vega.github.io/schema/vega-lite/v2.json",
"description": "A simple bar chart with embedded data.",
"width": 360,
"data": {"values": data},
"mark": "rect",
"encoding": {
"x": {"field": "L1", "type": "ordinal"},
"y": {"field": "L2", "type": "ordinal"}
}
})