Pulse Documentation

name: op-overlay-index-vs-prior
kind: operator
category: OVERLAY
operator: OVERLAY_INDEX_VS_PRIOR
description: Per-point streamable windowed index against the immediately preceding point of an ordered SERIES host (×100).
type: reference
applies_to: process, compose
examples_tags: [overlay, time-series, trend-detection, streaming-friendly]

Overlays decorate the host; no Response.Components.

Use when

Each point of an ordered series as an index value against the point before it (point / prior x 100): period-on-period change.

Questions it answers:

• By how much did sales grow or shrink from each month to the next?
• Is this week’s volume above or below last week’s, scaled to 100?

Use something else:

• OVERLAY_DELTA_VS_PRIOR when you want the change in the value’s own units.

Params

Scope must be group. Ref.Prior (object, empty) — implicit-default — empty Ref also accepted. Level/Within must be 0.

Host shape

SERIES — ordered grouped Process host. Family: windowed prior (Ref.Prior). First streamable windowed kind.

Output

SERIES — one SeriesEntry per host group key in host order, carrying index = point / prior × 100 on Summary.Statistic. Layer Baseline = 100.

Gotchas

• Single-state lag carrier (one float64) — streamable inside the streaming Process fold.
• NaN entries are statistic: null in JSON.
• First ordinal → NaN, no warning (“no comparison available” ≠ “denominator zero”).
• Absent host point → no statistic key + carrier does NOT advance (next present point still divides by last present value).
• Zero prior → NaN + ONE PULSE_OVERLAY_REF_ZERO per layer.
• Ref.Prior.Lag reserved for future window-N priors; v1 ships lag-1 only.
• Empty Ref and populated Ref.Prior both spell lag-1.
• Other Ref arms → PULSE_OVERLAY_REF_INCOMPATIBLE_WITH_SHAPE.
• Weighted host → weighted figure (reads the host payload).

See

• Skills: overlay-system, op-overlay-yoy, op-overlay-index-vs-rolling-mean.