Math — Chart: Cumulative Frequency

{
  "$schema": "https://vega.github.io/schema/vega-lite/v5.json",
  "description": "Cumulative frequency",
  "data": {"values": [
    {"upper": 10, "cf": 2},
    {"upper": 20, "cf": 9},
    {"upper": 30, "cf": 23},
    {"upper": 40, "cf": 43},
    {"upper": 50, "cf": 56},
    {"upper": 60, "cf": 62},
    {"upper": 70, "cf": 64}
  ]},
  "mark": {"type": "line", "point": true},
  "encoding": {
    "x": {"field": "upper", "type": "quantitative", "title": "upper class boundary"},
    "y": {"field": "cf", "type": "quantitative", "title": "cumulative frequency"}
  }
}