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        {"dir": "5S", "strength": 5},
        {"dir": "6SW", "strength": 6},
        {"dir": "7W", "strength": 7},
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      "from": {"data": "data_0"},
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          "fill": {"scale": "color", "field": "dir"},
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          "outerRadius": {"scale": "radius", "field": "strength_end"},
          "innerRadius": {"scale": "radius", "field": "strength_start"},
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        "data": "data_0",
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      "range": [0, {"signal": "min(width,height)/2"}],
      "zero": true
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      "name": "color",
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      "range": "category"
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}