Vega custom tooltip data visualisation

Question

Could anyone help be to develop a tooltip at line chart that looks like this?

Here is my spec at Vega Lite Editor.

Answer 1

Tooltips work on key:value pairs. If you amend your input data to an object of key value pairs and create a flatten transform, you can achieve your desired behaviour. I have changed all the tooltips below to be identical for speed but you should see the pattern.

{
  "description": "Total Count line chart.",
  "width": 1200,
  "height": 450,
  "padding": 5,
  "signals": [{"name": "interpolate", "value": "linear"}],
  "legends": [
    {
      "fill": "color",
      "orient": "bottom",
      "direction": "horizontal",
      "symbolType": "square"
    }
  ],
  "data": [
    {
      "name": "table",
      "values": [
        {
          "x": 0,
          "y": 30,
          "c": "Passenger Vessel",
          "tooltip": [
            {
              "title": "My Title",
              "Tall Ship": 0,
              "Sailing Yacht": 10,
              "Super Yacht": 20,
              "Motor Yacht": 10,
              "Rib": 0
            }
          ]
        },
        {
          "x": 1,
          "y": 20,
          "c": "Passenger Vessel",
          "tooltip": [
            {
              "title": "My Title",
              "Tall Ship": 0,
              "Sailing Yacht": 10,
              "Super Yacht": 20,
              "Motor Yacht": 10,
              "Rib": 0
            }
          ]
        },
        {
          "x": 2,
          "y": 90,
          "c": "Passenger Vessel",
          "tooltip": [
            {
              "Tall Ship": 0,
              "Sailing Yacht": 10,
              "Super Yacht": 20,
              "Motor Yacht": 10,
              "Rib": 0
            }
          ]
        },
        {
          "x": 3,
          "y": 60,
          "c": "Passenger Vessel",
          "tooltip": [
            {
              "title": "My Title",
              "Tall Ship": 0,
              "Sailing Yacht": 10,
              "Super Yacht": 20,
              "Motor Yacht": 10,
              "Rib": 0
            }
          ]
        },
        {
          "x": 4,
          "y": 50,
          "c": "Passenger Vessel",
          "tooltip": [
            {
              "title": "My Title",
              "Tall Ship": 0,
              "Sailing Yacht": 10,
              "Super Yacht": 20,
              "Motor Yacht": 10,
              "Rib": 0
            }
          ]
        },
        {
          "x": 5,
          "y": 40,
          "c": "Passenger Vessel",
          "tooltip": [
            {
              "title": "My Title",
              "Tall Ship": 0,
              "Sailing Yacht": 10,
              "Super Yacht": 20,
              "Motor Yacht": 10,
              "Rib": 0
            }
          ]
        },
        {
          "x": 6,
          "y": 10,
          "c": "Passenger Vessel",
          "tooltip": [
            {
              "title": "My Title",
              "Tall Ship": 0,
              "Sailing Yacht": 10,
              "Super Yacht": 20,
              "Motor Yacht": 10,
              "Rib": 0
            }
          ]
        },
        {
          "x": 0,
          "y": 50,
          "c": "Pleasure Craft",
          "tooltip": [
            {
              "title": "My Title",
              "Tall Ship": 0,
              "Sailing Yacht": 10,
              "Super Yacht": 20,
              "Motor Yacht": 10,
              "Rib": 0
            }
          ]
        },
        {
          "x": 1,
          "y": 10,
          "c": "Pleasure Craft",
          "tooltip": [
            {
              "title": "My Title",
              "Tall Ship": 0,
              "Sailing Yacht": 10,
              "Super Yacht": 20,
              "Motor Yacht": 10,
              "Rib": 0
            }
          ]
        },
        {
          "x": 2,
          "y": 50,
          "c": "Pleasure Craft",
          "tooltip": [
            {
              "Tall Ship": 0,
              "Sailing Yacht": 10,
              "Super Yacht": 20,
              "Motor Yacht": 10,
              "Rib": 0
            }
          ]
        },
        {
          "x": 3,
          "y": 40,
          "c": "Pleasure Craft",
          "tooltip": [
            {
              "title": "My Title",
              "Tall Ship": 0,
              "Sailing Yacht": 10,
              "Super Yacht": 20,
              "Motor Yacht": 10,
              "Rib": 0
            }
          ]
        },
        {
          "x": 4,
          "y": 110,
          "c": "Pleasure Craft",
          "tooltip": [
            {
              "title": "My Title",
              "Tall Ship": 0,
              "Sailing Yacht": 10,
              "Super Yacht": 20,
              "Motor Yacht": 10,
              "Rib": 0
            }
          ]
        },
        {
          "x": 5,
          "y": 40,
          "c": "Pleasure Craft",
          "tooltip": [
            {
              "title": "My Title",
              "Tall Ship": 0,
              "Sailing Yacht": 10,
              "Super Yacht": 20,
              "Motor Yacht": 10,
              "Rib": 0
            }
          ]
        },
        {
          "x": 6,
          "y": 20,
          "c": "Pleasure Craft",
          "tooltip": [
            {
              "title": "My Title",
              "Tall Ship": 0,
              "Sailing Yacht": 10,
              "Super Yacht": 20,
              "Motor Yacht": 10,
              "Rib": 0
            }
          ]
        },
        {"x": 0, "y": 50, "c": "Unknown", "tooltip": [{}]},
        {"x": 1, "y": 60, "c": "Unknown", "tooltip": [{}]},
        {"x": 2, "y": 90, "c": "Unknown", "tooltip": [{}]},
        {"x": 3, "y": 40, "c": "Unknown", "tooltip": [{}]},
        {"x": 4, "y": 50, "c": "Unknown", "tooltip": [{}]},
        {"x": 5, "y": 20, "c": "Unknown", "tooltip": [{}]},
        {"x": 6, "y": 40, "c": "Unknown", "tooltip": [{}]}
      ],
      "transform": [{"type": "flatten", "fields": ["tooltip"]}]
    }
  ],
  "scales": [
    {
      "name": "x",
      "type": "point",
      "range": "width",
      "domain": {"data": "table", "field": "x"}
    },
    {
      "name": "y",
      "type": "linear",
      "range": "height",
      "nice": true,
      "zero": true,
      "domain": {"data": "table", "field": "y"}
    },
    {
      "name": "color",
      "type": "ordinal",
      "range": ["#BA20CE", "#60cf85", "#cd2c4f"],
      "domain": {"data": "table", "field": "c"}
    }
  ],
  "axes": [
    {"orient": "bottom", "scale": "x"},
    {"orient": "left", "scale": "y"}
  ],
  "config": {
    "style": {
      "guide-label": {"fontSize": 14, "fill": "#cccccc", "fontWeight": 800}
    },
    "axis": {"grid": true, "gridColor": "#333333"}
  },
  "marks": [
    {
      "type": "group",
      "from": {"facet": {"name": "series", "data": "table", "groupby": "c"}},
      "marks": [
        {
          "type": "line",
          "from": {"data": "series"},
          "encode": {
            "enter": {
              "x": {"scale": "x", "field": "x"},
              "y": {"scale": "y", "field": "y"},
              "stroke": {"scale": "color", "field": "c"},
              "strokeWidth": {"value": 2}
            },
            "update": {
              "interpolate": {"signal": "interpolate"},
              "strokeOpacity": {"value": 1}
            },
            "hover": {"strokeOpacity": {"value": 0.5}}
          }
        },
        {
          "type": "symbol",
          "from": {"data": "series"},
          "encode": {
            "update": {
              "x": {"scale": "x", "field": "x"},
              "y": {"scale": "y", "field": "y"},
              "fillOpacity": {"value": 0}
            },
            "hover": {
              "fillOpacity": {"value": 1},
              "fill": {"scale": "color", "field": "c"},
              "cursor": {"value": "pointer"},
              "tooltip": {"signal": "datum['tooltip'] "}
            }
          }
        }
      ]
    }
  ]
}