https://vega.github.io/editor/#/examples/vega-lite/overview_detailはconcatを使用しています。
{
"$schema": "https://vega.github.io/schema/vega-lite/v2.json",
"data": {"url": "data/sp500.csv"},
"vconcat": [{
"width": 480,
"mark": "area",
"encoding": {
"x": {
"field": "date",
"type": "temporal",
"scale": {"domain": {"selection": "brush"}},
"axis": {"title": "", "labelAngle": 0}
},
"y": {"field": "price","type": "quantitative"}
}
}, {
"width": 480,
"height": 60,
"mark": "area",
"selection": {
"brush": {"type": "interval", "encodings": ["x"]}
},
"encoding": {
"x": {
"field": "date",
"type": "temporal",
"axis": {"format": "%Y", "labelAngle": 0}
},
"y": {
"field": "price",
"type": "quantitative",
"axis": {"tickCount": 3, "grid": false}
}
}
}]
}