{
  "$schema": "https://vega.github.io/schema/vega/v3.0.json", 
  "config":{"background":"#ffffff"},
  "width": 800,
  "height": 480,
  "autosize": "none",
  "projections": [
    {
      "name": "projection",
      "type": "albersUsa",
      "scale": 900,
      "translate": [{"signal": "width / 2"},{"signal": "height / 2"}]
    }
  ],
  "data": [
    {
      "name": "states",
      "url": "data/us-10m.json",
      "format": {"type": "topojson","feature": "states"},
      "transform": [{"type": "geopath","projection": "projection"}]
    },
    {
      "name": "zipcodes",
      "url": "data/zip_codes_states.csv",
      "format": {
        "type": "csv",
        "parse": {
          "longitude": "number",
          "latitude": "number",
          "zip_code": "string"
        }
      },
      "transform": [
        {
          "type": "formula",
          "expr": "substring(datum.zip_code, 0, 1)",
          "as": "digit"
        },
        {
          "type": "geopoint",
          "projection": "projection",
          "fields": ["longitude","latitude"]
        }
      ]
    }
  ],
  "scales": [
    {
      "name": "color",
      "type": "ordinal",
      "domain": {"data": "zipcodes","field": "digit", "sort": true},
      "range": "category"
    }
  ],
  "legends": [{"fill": "color", "orient": "top-right"}],
  "marks": [
    {
      "type": "path",
      "from": {"data": "states"},
      "encode": {
        "enter": {
          "strokeWidth": {"value": "1"},
          "stroke": {"value": "#fff"},
          "fill": {"value": "#ddd"},
          "path": {"field": "path"}
        }
      }
    },
    {
      "type": "symbol",
      "interactive": false,
      "from": {"data": "zipcodes"},
      "encode": {
        "enter": {
          "size": {"value": 2},
          "shape": {"value": "circle"},
          "fill": {"scale": "color","field": "digit"}
        },
        "update": {"x": {"field": "x"},"y": {"field": "y"}}
      }
    }
  ]
}