How to combine multi timelines in one vega graph using layers

[bab (Broou)]

hi experts, am trying to combine multi time lines Vega graphic to one but i'm stock, can anyone check my code, where i missed.

{
  $schema: https://vega.github.io/schema/vega-lite/v2.json
  data: {
    url: {
      %context%: true
      %timefield%: Date
      index: index_tev_test
      body: {
        size: 4000
        _source: [
          Date,
          Basis,
          FT1,
          FT2
        ]
      }
    }
    format: {
      property: hits.hits
    }
  }
  mark: {
    type: line
    point: true
  }
  encoding: {
    x: {
      field: _source.Date
      type: nominal
      sort: 0
      axis: {
        title: Date
      }
    }
    order: {
      field: Date
    }
  }
  layer: [
    {
      mark: line
      encoding: {
        y: {
          field: _source.Basis
          type: nominal
          axis: {
            title: Basis
          }
        }
        color: {
          value: red
        }
      }
    }
    {
      mark: line
      encoding: {
        y: {
          field: _source.FT1
          type: nominal
          axis: {
            title: FT1
          }
        }
        color: {
          value: blue
        }
      }
    }
    {
      mark: line
      encoding: {
        y: {
          field: _source.FT2
          type: nominal
          axis: {
            title: FT2
          }
        }
        color: {
          value: green
        }
      }
    }
  ]
}

the result for the above code is:

[nickofthyme (Nick Partridge)]

There seems to be something wrong with your x encoding as the value is undefined. Could be that the type as a date should be temporal not nominal.

Could you provide a demo on the Vega Editor, like this, using a sample raw dataset with values, something like...

{
  data: {"name": "table", "values": [12, 23, 47, 6, 52, 19]}
}

Then I can take a closer look.