Vega-Lite spec from Fri Aug 21 2020

spec.json

{
  "$schema": "https://vega.github.io/schema/vega-lite/v4.json",
  "data": {
    "values":[
      {"date": "2020-08-01", "retention":2341},
      {"date": "2020-08-02", "retention":1234},
      {"date": "2020-08-03", "retention":1101},
      {"date": "2020-08-04", "retention":998},
      {"date": "2020-08-05", "retention":543},
      {"date": "2020-08-06", "retention":589},
      {"date": "2020-08-07", "retention":660},
      {"date": "2020-08-08", "retention":421},
      {"date": "2020-08-09", "retention":321},
      {"date": "2020-08-10", "retention":309},
      {"date": "2020-08-11", "retention":211},
      {"date": "2020-08-12", "retention":129},
      {"date": "2020-08-13", "retention":110},
      {"date": "2020-08-14", "retention":89},
      {"date": "2020-08-15", "retention":34},
      {"date": "2020-08-16", "retention":21},
      {"date": "2020-08-17", "retention":19},
      {"date": "2020-08-18", "retention":5}
    ]
  },
  "mark": "bar",
  "encoding": {
    "y": {"field": "retention", "type": "quantitative", "title": "留存用户数"},
    "x": { "field": "date", "title": "日期"}
  }
}