Sleep Regularity Index

SRI formula:
SRI = −100 + (200 / (M × (N−1))) × Σ matches
M = epochs/day (48 × 30-min), N = days, matches = consecutive days in same state

Reference:
Fischer D, Klerman EB, Phillips AJK. (2021). “Measuring sleep regularity: theoretical properties and practical usage of existing metrics.” Sleep. PMC8503839