Tasa de variación: pipeline derivative

{
  "$schema": "https://vega.github.io/schema/vega-lite/v5.json",
  "data": {
    "values": [
      { "key": "2026-06-08T09:00:00", "deriv": null },
      { "key": "2026-06-08T09:05:00", "deriv": { "value": 32 } },
      { "key": "2026-06-08T09:10:00", "deriv": { "value": -18 } },
      { "key": "2026-06-08T09:15:00", "deriv": { "value": 124 } },
      { "key": "2026-06-08T09:20:00", "deriv": { "value": 260 } },
      { "key": "2026-06-08T09:25:00", "deriv": { "value": -340 } },
      { "key": "2026-06-08T09:30:00", "deriv": { "value": -85 } },
      { "key": "2026-06-08T09:35:00", "deriv": { "value": 42 } },
      { "key": "2026-06-08T09:40:00", "deriv": { "value": 96 } },
      { "key": "2026-06-08T09:45:00", "deriv": { "value": -54 } }
    ]
  },
  "transform": [{ "calculate": "datum.deriv ? datum.deriv.value : 0", "as": "delta" }],
  "mark": "bar",
  "encoding": {
    "x": { "field": "key", "type": "temporal", "title": null },
    "y": { "field": "delta", "type": "quantitative", "title": "Δ docs / bucket" },
    "color": {
      "condition": { "test": "datum.delta >= 0", "value": "#2e7d32" },
      "value": "#c62828"
    }
  }
}