SETPOINTk.ai · Metric Surface

SPI · Definition

SPI (SETPOINT Index) is a longitudinal composite signal describing regulation stability across time. SPI is not a single measurement; it models trajectory, recovery behavior, adaptive variability, and baseline drift.

What SPI is

A time-series composite derived from rolling feature windows.
A regulation surface: stability, recovery slope, variability bandwidth, and drift.
A deterministic interpretation grammar for longitudinal behavior (not a diagnosis).

What SPI is not

Not a diagnostic test, disease classifier, or treatment recommendation.
Not a replacement for clinician judgment or validated clinical instruments.
Not a single “target value” — it is interpreted as behavior across time.

Conceptual architecture

SPI Concept Diagram (placeholder)

Inputs → Feature windows → Composite surface → Zone interpretation

Gold-Blue Surface

Inputs

HRV · Sleep · Activity · Recovery

Windows

rolling bands · slopes · dispersion

Surface

stability · variability · drift

Zones

stable · recovering · volatile · drifting

Public-safe composite form

SPI is composed from normalized longitudinal features. Exact weighting and transforms are internal.

SPI(t) = f(
  stability(t),
  recovery(t),
  variability(t),
  baseline_drift(t)
)

Why trajectories matter (vs snapshots)

Two people can share the same snapshot reading (e.g., resting heart rate) while exhibiting very different longitudinal behavior.

Recovery: how quickly physiology returns toward baseline after perturbation.
Variability: whether the system stays within a stable adaptive bandwidth.
Drift: whether the baseline shifts over days/weeks (direction + magnitude).

Snapshots measure state. SPI measures behavior across time.

Governance boundary

SPI is an educational and analytical signal surface. It does not diagnose, treat, cure, or prevent disease. Clinical decisions require licensed medical evaluation and validated clinical workflows.

If you are experiencing urgent symptoms, seek professional medical care.