{
  "$schema": "urn:prism:schema:v1:spec",
  "title": "Explicit stack transform, bound as a y span",
  "data": {
    "values": [
      {"stage": "trial", "plan": "business", "users": 260},
      {"stage": "active", "plan": "business", "users": 340},
      {"stage": "churned", "plan": "business", "users": 60},
      {"stage": "trial", "plan": "team", "users": 410},
      {"stage": "active", "plan": "team", "users": 280},
      {"stage": "churned", "plan": "team", "users": 95}
    ]
  },
  "transform": [
    {
      "stack": "users",
      "groupby": ["stage"],
      "offset": "zero",
      "as": ["users_lo", "users_hi"]
    }
  ],
  "mark": "bar",
  "encoding": {
    "x": {"field": "stage", "type": "nominal"},
    "y": {"field": "users_lo", "type": "quantitative", "axis": {"title": "users"}},
    "y2": {"field": "users_hi", "type": "quantitative"},
    "color": {"field": "plan", "type": "nominal"}
  }
}