Table Bubble Plot (Github Punch Card)

{
  "$schema": "https://vega.github.io/schema/vega-lite/v2.json",
  "description": "Punchcard Visualization like on Github. The day on y-axis uses a custom order from Monday to Sunday.  The sort property supports both full day names (e.g., 'Monday') and their three letter initials (e.g., 'mon') -- both of which are case insensitive.",
  "data": { "url": "data/github.csv"},
  "mark": "circle",
  "encoding": {
    "y": {
      "field": "time",
      "type": "ordinal",
      "timeUnit": "day",
      "sort": ["mon", "tue", "wed", "thu", "fri", "sat", "sun"]
    },
    "x": {
      "field": "time",
      "type": "ordinal",
      "timeUnit": "hours"
    },
    "size": {
      "field": "count",
      "type": "quantitative",
      "aggregate": "sum"
    }
  }
}