feat(psychometric): recover Hamaker Eq. 1a occasion-mean event-time lag

CHANGELOG.md

@@ -38,6 +38,8 @@ All notable changes to TEPP are documented here. The format follows Keep a Chang
 
 ## [Unreleased]
 
+- `psychometric_core` recovers Hamaker, Kuiper, and Grasman (2015, Eq. 1a–1d; UvA-DARE PDF opened 2026-09-03T06:07Z KST from https://dare.uva.nl) occasion-mean-centered event-time lags. The CLPM measurement equation is `x_it = μ_t + p_it` where `μ_t` is the grand mean at occasion `t`, not the sample-wide grand mean and not the person mean. The temporal deviations `p_it` still contain trait-like between-person differences; lagged relations on those residuals are not within-person. This slice forms `p_it` on aligned event-time waves, maps consecutive residuals through the exact scalar log-rate `a = ln(p_{i,t}/p_{i,t-1}) / Δt` (Voelkle et al., 2012, Eq. 7), and refuses treating that rate as a within-person lag. Consecutive aligned waves may have unequal spacing. Unaligned event times have no shared occasion and fail closed. This is not RI-CLPM (Hamaker et al., 2015, Eq. 3a), not DSEM, not CWC, and not the open `#332` sample-grand-mean lag. Meredith (1993) remains unread (Unpaywall 2026-09-03T06:07Z KST: `is_oa: false`). Mislevy (1991, *Psychometrika, 56*, 177–196) remains unread on the same terms (DOI `10.1007/bf02294457`; Unpaywall `is_oa: false`).
+
 - `event_core` adds bounded Allen interval-consistency classification, atomic path-consistency closure, contradiction/resource refusals, and an explicit dependency-error fallback without claiming unrestricted global satisfiability.
 
 - `psychometric_core` recovers the Driver, Oud, and Voelkle (2017, Table 2, p. 12 `MANIFESTTRAITVAR`; §7.1, p. 19; p. 16 `MANIFESTTRAITVARstd`; footnote 4; 2017-era ctsem `summary.ctsemFit.R`; JSS PDF re-opened 2026-08-27T14:20Z from https://www.jstatsoft.org/index.php/jss/article/download/v077i05/1104) scalar standardised manifest-trait variance on current main after `0ce16e8` dropped the pre-consolidation code while research notes already named the map (register items 83–84). Table 2 names `MANIFESTTRAITVAR` `Ψ_τ` the additional time-invariant variance-covariance on the measurement level and sets it `NULL` when there is no manifest trait. Equation 5 writes `Γ ~ N(τ, Ψ)` and names that covariance the manifest traits. Section 7.1 names manifest traits stable individual differences in indicator levels, distinct from process-level `TRAITVAR` `φ_ξ`. Page 16 prints standardised matrices with the suffix `std` when appropriate. The printed example on p. 16 is `discreteDRIFTstd`, not `MANIFESTTRAITVARstd`. Footnote 4 standardises using only the relevant variance, not the total. The relevant variance for that named indicator-level correlation is `MANIFESTTRAITVAR`, not process-level `TRAITVAR` and not residual `MANIFESTVAR` `θ`. The 2017-era source forms `MANIFESTTRAITVARstd` only when `MANIFESTTRAITVAR != 0`, as `solve(sqrt(diag(MANIFESTTRAITVAR) + ridging)) %&% MANIFESTTRAITVAR` when `verbose = TRUE`. OpenMx `%&%` is `t(A) %*% B %*% A`. Unlike `TRAITVARstd`, that formation adds `diag(c(ridging), n.manifest)`. The default `ridging = FALSE` adds 0, not `0.0001`; that ridge is a numerical hack and is not this exact map. The scalar correlation is `ψ / ψ = 1` after strictly positive `MANIFESTTRAITVAR`. Form strictly positive `ψ` first, then `1 / √ψ`, then `(1 / √ψ) ψ (1 / √ψ)`. Unstandardised `MANIFESTTRAITVAR` is defined for a zero trait; standardised `MANIFESTTRAITVAR` is not. Zero `MANIFESTTRAITVAR` skips forming `MANIFESTTRAITVARstd` in the 2017-era source and fails closed here. Indicator-level trait variance is an event-time structural quantity, so a non-event clock fails closed. `MANIFESTTRAITVAR` does not require stable `a < 0`. Distinct positive `ψ` recover the same 1. `trait / trait = 1` is `TRAITVARstd` and recovers the same number and remains a distinct named quantity. `θ` is `MANIFESTVAR` and is measurement error, not this correlation. Meredith (1993) remains unread (web search 2026-08-27T14:20Z: Springer/Cambridge Core paywalled; Unpaywall historically `is_oa: false`; Springer `content/pdf` is an HTML stub). Mislevy (1991, *Psychometrika, 56*, 177–196) remains unread on the same terms (DOI `10.1007/bf02294457`). Still not a Kalman filter, not a matrix `expm`, not ESEM estimation, not DSEM, and not ctsem estimation.

crates/psychometric_core/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "psychometric_core"
-description = "Posterior-aware ESEM/DSEM input gates, multilevel/event-time recovery, CWC contextual effect, Voelkle Eqs. 12 and 14, Driver Eq. 3 TDPRED/TIPRED maps including within-interval impulse carry, Rubin T, and strong-invariance latent means."
+description = "Posterior-aware ESEM/DSEM input gates, multilevel/event-time recovery, CWC contextual effect, Hamaker Eq. 1a occasion-mean residual lag (not within-person), Voelkle Eqs. 12 and 14, Driver Eq. 3 TDPRED/TIPRED maps including within-interval impulse carry, Rubin T, and strong-invariance latent means."
 version.workspace = true
 edition.workspace = true
 rust-version.workspace = true

crates/psychometric_core/src/error.rs

@@ -710,6 +710,12 @@ pub enum PsychometricError {
     /// `MANIFESTVARstd`. `λ² Var(η) + θ` is `Var(y)`, not the
     /// correlation form of `Θ`.
     ObservedVarianceIsNotStandardisedManifestVariance,
+    /// Hamaker, Kuiper, and Grasman (2015, Eq. 1a–1d) occasion-mean
+    /// residuals `p_it = x_it − μ_t` were treated as within-person
+    /// residuals. Those temporal deviations still contain trait-like
+    /// between-person differences from the time-varying group mean.
+    /// This is not RI-CLPM (their Eq. 3a).
+    OccasionMeanCenteredLagIsNotWithinPerson,
 }
 
 impl fmt::Display for PsychometricError {
@@ -1235,6 +1241,9 @@ impl fmt::Display for PsychometricError {
             Self::ObservedVarianceIsNotStandardisedManifestVariance => {
                 "observed-indicator variance is not standardised measurement-error variance"
             }
+            Self::OccasionMeanCenteredLagIsNotWithinPerson => {
+                "occasion-mean-centered lag is not a within-person lag"
+            }
         };
         formatter.write_str(message)
     }
@@ -2073,4 +2082,12 @@ mod tests {
             "measurement error is not standardised manifest-trait variance"
         );
     }
+
+    #[test]
+    fn occasion_mean_centered_lag_boundary_message_is_stable() {
+        assert_eq!(
+            PsychometricError::OccasionMeanCenteredLagIsNotWithinPerson.to_string(),
+            "occasion-mean-centered lag is not a within-person lag"
+        );
+    }
 }