Choropleth of unemployment rate per county

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Vega-Lite JSON Specification

{
  "$schema": "https://vega.github.io/schema/vega-lite/v3.json",
  "width": 500,
  "height": 300,
  "data": {
    "url": "data/us-10m.json",
    "format": {
      "type": "topojson",
      "feature": "counties"
    }
  },
  "transform": [{
    "lookup": "id",
    "from": {
      "data": {
        "url": "data/unemployment.tsv"
      },
      "key": "id",
      "fields": ["rate"]
    }
  }],
  "projection": {
    "type": "albersUsa"
  },
  "mark": "geoshape",
  "encoding": {
    "color": {
      "field": "rate",
      "type": "quantitative"
    }
  }
}