Cookbook: faceting by data values

Render one mini-chart per partition of a categorical field.

Spec

{
  "$schema": "urn:prism:schema:v1:spec",
  "data": {"source": "cohorts/q1.pulse"},
  "facet": {"column": {"field": "region"}},
  "spec": {
    "$schema": "urn:prism:schema:v1:spec",
    "mark": "bar",
    "encoding": {
      "x": {"field": "brand_id", "type": "nominal"},
      "y": {"field": "score", "type": "quantitative", "aggregate": "mean"}
    }
  },
  "resolve": {"scale": {"y": "shared"}}
}

Notes

• The upstream Source + transform pipeline runs once; the resulting Table is partitioned at encode time.
• resolve.scale.y: shared (default for facet) computes the union y-domain so cells are visually comparable. Use independent for per-cell domains.
• Nested facets work (facet within facet within facet) — the inner spec field is recursive.
• For grid by field list instead of by data values, use repeat.