`rolling_stddev`

Generic Description

Computes trailing standard deviation over a fixed-size window. It is documented separately because time construction, sequence ordering, window parameters, and as-of behavior materially change analytical meaning.

Simple example:

WITH [10.0, 13.0, 9.0, 16.0] AS readings
RETURN rolling_stddev(readings, 3) AS trailing_volatility

Consumer-Level Explanation

Use it when instability in the recent frame matters as much as the level. Prefer this function when the temporal assumption should be visible to the planner, especially for event streams, freshness checks, and sequence features.

More Detailed Explanation

rolling_stddev works on ordered temporal or sequence-style values inside Cypher. The practical contract is to assemble the sequence deliberately, choose the time or window parameter explicitly, and return named fields so downstream planner tooling does not invent unsupported window syntax.

Advanced Example

This example names the event stream and operational context before applying rolling_stddev, which helps planner tooling preserve the intended sequence semantics.

WITH 'sensor-1' AS subject_id,
     [{ts: 1735689600000, value: 10.0, state: 'ok'}, {ts: 1735689660000, value: 13.0, state: 'ok'}, {ts: 1735689840000, value: 9.0, state: 'warn'}, {ts: 1735690200000, value: 16.0, state: 'ok'}] AS readings
RETURN subject_id,
       rolling_stddev(readings, 3) AS trailing_volatility

Real Use Cases

Real Limitations And Tradeoffs