concat_hover_filter.vl.json

{
  "$schema": "https://vega.github.io/schema/vega-lite/v4.json",
  "description": "Drag out a rectangular brush to highlight points.",
  "data": {"url": "data/cars.json"},
  "hconcat": [{
    "encoding": {
      "x": {"field": "Horsepower", "type": "quantitative"},
      "y": {"field": "Miles_per_Gallon", "type": "quantitative"}
    },
    "layer": [
      {
        "params": [{
          "name": "hover",
          "select": {
            "type": "single",
            "on": "mouseover",
            "empty": "none"
          }
        }],
        "mark": "point"
      },
      {
        "mark": {"type": "point", "color": "goldenrod"},
        "transform": [{"filter": {"selection": "hover"}}]
      }
    ]
  }, {
    "encoding": {
      "x": {"field": "Horsepower", "type": "quantitative"},
      "y": {"field": "Acceleration", "type": "quantitative"}
    },
    "layer": [
      {

        "params": [{
          "name": "hover",
          "select": {
            "type": "single",
            "on": "mouseover",
            "empty": "none"
          }
        }],
        "mark": "point"
      },
      {
        "mark": {"type": "point", "color": "goldenrod"},
        "transform": [{"filter": {"selection": "hover"}}]
      }
    ]
  }]
}