feat(psychometric): recover Driver p.16 asymCINTstd after positive p

CHANGELOG.md

@@ -4,6 +4,7 @@ All notable changes to TEPP are documented here. The format follows Keep a Chang
 
 ## [Unreleased]
 
+- `psychometric_core` recovers the Driver, Oud, and Voelkle (2017, p. 16 `asymCINTstd`; Eq. 3, p. 4; footnote 4; Table 2, p. 12; 2017-era ctsem `summary.ctsemFit.R`; JSS PDF re-opened 2026-08-24T09:05Z from https://www.jstatsoft.org/index.php/jss/article/download/v077i05/1104) scalar standardised asymptotic continuous intercept. Page 16 prints standardised matrices with the suffix `std` when appropriate. Footnote 4 standardises using only the relevant variance, not the total. `CINT` is the process intercept of individual, or average individual, dynamics, so that relevant variance is within-subject `asymDIFFUSION` `p = −q / (2 a)`. The 2017-era `summary.ctsemFit.R` forms `asymCINT` whenever `verbose = TRUE`, as `-solve(DRIFT) %*% CINT`. That source does not form an `asymCINTstd` matrix; the scalar map here is the footnote 4 standardisation of that named asymptotic intercept: `(-κ / a) / √p`. Form strictly positive `p` first, then the asymptotic intercept, then divide by `√p`. A zero intercept is exactly zero. Unstandardised `asymCINT` is defined for a zero process; standardised `asymCINT` is not. Zero `q` has no positive process SD and fails closed. Lasting `asymDIFFUSION` requires stable `a < 0`. A non-event clock fails closed. `κ / √p` is the continuous intercept standardisation and is not this total-change map. `A^{-1}[e^{A Δt} − I] κ / √p` depends on the event interval and is not this `Δt → ∞` map. Still not a Kalman filter, not a matrix `expm`, not ESEM estimation, not DSEM, not `CINTstd`, not `discreteCINTstd`, and not ctsem estimation. Meredith (1993) remains unread (Unpaywall 2026-08-24T08:02Z: `is_oa: false`, 0 locations; title *Measurement Invariance, Factor Analysis and Factorial Invariance*). Mislevy (1991, *Psychometrika, 56*, 177–196) remains unread (Unpaywall 2026-08-24T08:02Z: `is_oa: false`, 0 locations; title *Randomization-Based Inference about Latent Variables from Complex Samples*).
 - `psychometric_core` recovers the Driver, Oud, and Voelkle (2017, p. 16 `discreteCINTstd`; Eq. 3, p. 4; footnote 4; Table 2, p. 12; 2017-era ctsem `summary.ctsemFit.R`; JSS PDF re-opened 2026-08-24T05:20Z from https://www.jstatsoft.org/index.php/jss/article/download/v077i05/1104) scalar standardised discrete continuous intercept. Page 16 prints discrete-time transformations for a chosen event interval and, when appropriate, standardised matrices with the suffix `std`. Footnote 4 standardises using only the relevant variance, not the total. `CINT` is the process intercept of individual, or average individual, dynamics, so that relevant variance is within-subject `asymDIFFUSION` `p = −q / (2 a)`. The 2017-era `summary.ctsemFit.R` forms `discreteCINT` whenever `verbose = TRUE`, as `solve(DRIFT) %*% (discreteDRIFT − I) %*% CINT`. That source does not form a `discreteCINTstd` matrix; the scalar map here is the footnote 4 standardisation of that named discrete intercept: `A^{-1}[e^{A Δt} − I] κ / √p`. Form strictly positive `p` first, then the discrete intercept, then divide by `√p`. A zero intercept is exactly zero. Unstandardised `discreteCINT` is defined for growing `a ≥ 0` and for zero diffusion; standardised `discreteCINT` is not. Zero `q` has no positive process SD and fails closed. Lasting `asymDIFFUSION` requires stable `a < 0`. A non-event clock fails closed. A non-positive event interval fails closed. `κ / √p` does not depend on `Δt` and is not this finite-interval map. `(-κ / a) / √p` is the standardised asymptotic intercept and is not this map. Still not a Kalman filter, not a matrix `expm`, not ESEM estimation, not DSEM, not `CINTstd`, and not ctsem estimation. Meredith (1993) remains unread (Unpaywall 2026-08-24T08:02Z: `is_oa: false`, 0 locations; title *Measurement Invariance, Factor Analysis and Factorial Invariance*). Mislevy (1991, *Psychometrika, 56*, 177–196) remains unread (Unpaywall 2026-08-24T08:02Z: `is_oa: false`, 0 locations; title *Randomization-Based Inference about Latent Variables from Complex Samples*).
 - `psychometric_core` recovers the Driver, Oud, and Voelkle (2017, p. 16 `asymDIFFUSIONstd`; footnote 4; Eq. 4; 2017-era ctsem `summary.ctsemFit.R`; JSS PDF re-opened 2026-08-23T23:02Z from https://www.jstatsoft.org/index.php/jss/article/download/v077i05/1104) scalar standardised asymptotic within-subject variance. Page 16 names `asymDIFFUSION` the total within-subject variance as `Δt → ∞` and prints standardised matrices with the suffix `std` when appropriate. Footnote 4 standardises using only the relevant variance, not the total. The 2017-era `summary.ctsemFit.R` forms `asymDIFFUSIONstd` whenever `verbose = TRUE`, as `solve(sqrt(diag(asymDIFFUSION) + ridging)) %&% asymDIFFUSION`. OpenMx `%&%` is the quadratic form `t(A) %*% B %*% A`. That formation adds `diag(c(ridging), n.latent)`. The default `ridging = FALSE` adds 0, not `0.0001`; that ridge is a numerical hack and is not this exact map. The 2017-era source assigns `dimnames(asymDIFFUSIONstd)` to `latentNames`; that assignment matches the `n.latent × n.latent` matrix and is this map. The scalar correlation is `p / p = 1` after strictly positive Lyapunov `p = −q / (2 a)`. Form strictly positive `p` first, then `1 / √p`, then `(1 / √p) p (1 / √p)`. Unstandardised `asymDIFFUSION` is defined for a zero process; standardised `asymDIFFUSION` is not. Zero `q` makes `solve(sqrt(0))` fail in the 2017-era source and fails closed here. That source does not skip forming `asymDIFFUSIONstd` when `p = 0`. Within-subject variance is an event-time structural quantity, so a non-event clock fails closed. Lasting `asymDIFFUSION` requires stable `a < 0`. Distinct positive `p` recover the same 1. `TIPREDVARstd` `v / v = 1` recovers the same number and remains a distinct named quantity. `DIFFUSIONstd` `q / p = −2 a` is the continuous-diffusion ratio, not this correlation. Still not a Kalman filter, not a matrix `expm`, not ESEM estimation, not DSEM, and not ctsem estimation. Meredith (1993) remains unread (Unpaywall 2026-08-24T08:02Z: `is_oa: false`, 0 locations; title *Measurement Invariance, Factor Analysis and Factorial Invariance*). Mislevy (1991, *Psychometrika, 56*, 177–196) remains unread (Unpaywall 2026-08-24T08:02Z: `is_oa: false`, 0 locations; title *Randomization-Based Inference about Latent Variables from Complex Samples*).
 - `psychometric_core` recovers the Driver, Oud, and Voelkle (2017, Table 2, p. 12 `TIPREDVAR`; p. 16 `TIPREDVARstd`; footnote 4; 2017-era ctsem `summary.ctsemFit.R`; JSS PDF re-opened 2026-08-23T22:53Z from https://www.jstatsoft.org/index.php/jss/article/download/v077i05/1104) scalar standardised time-independent predictor variance. Table 2 names `TIPREDVAR` the variance/covariance of time-independent predictors. Page 16 prints standardised matrices with the suffix `std` when appropriate. The 2017-era `summary.ctsemFit.R` forms `TIPREDVARstd` whenever `verbose = TRUE` and `n.TIpred > 0`, as `solve(sqrt(diag(TIPREDVAR) + ridging)) %&% TIPREDVAR`. OpenMx `%&%` is the quadratic form `t(A) %*% B %*% A`. Unlike `TRAITVARstd`, that formation adds `diag(c(ridging), n.TIpred)`. The default `ridging = FALSE` adds 0, not `0.0001`; that ridge is a numerical hack and is not this exact map. The 2017-era source assigns `dimnames(TIPREDVARstd)` to `TIpredNames`; that assignment matches the `n.TIpred × n.TIpred` matrix and is this map. The scalar correlation is `v / v = 1` after strictly positive `TIPREDVAR`. Form strictly positive `v` first, then `1 / √v`, then `(1 / √v) v (1 / √v)`. Unstandardised `TIPREDVAR` is defined for a zero predictor; standardised `TIPREDVAR` is not. Zero `v` makes `solve(sqrt(0))` fail in the 2017-era source and fails closed here. Unlike `TRAITVAR` / `MANIFESTTRAITVAR`, that source does not skip forming `TIPREDVARstd` when `v = 0`. Predictor variance is an event-time structural quantity, so a non-event clock fails closed. `TIPREDVAR` does not require stable `a < 0`. Distinct positive `v` recover the same 1. `MANIFESTVARstd` `θ / θ = 1` recovers the same number and remains a distinct named quantity. Section 7.2 `addedTIPREDVAR` `(B / a)² v` is extra process variance, not this correlation. Still not a Kalman filter, not a matrix `expm`, not ESEM estimation, not DSEM, and not ctsem estimation. Meredith (1993) remains unread (Unpaywall 2026-08-23T22:21Z: `is_oa: false`; title *Measurement Invariance, Factor Analysis and Factorial Invariance*). Mislevy (1991, *Psychometrika, 56*, 177–196) remains unread (Unpaywall 2026-08-23T22:21Z: `is_oa: false`; title *Randomization-Based Inference about Latent Variables from Complex Samples*).

crates/psychometric_core/src/error.rs

@@ -1061,6 +1061,24 @@ pub enum PsychometricError {
     /// `discreteCINTstd`. `(-κ / a) / √p` is the standardised
     /// total intercept change, not the finite-interval map.
     AsymptoticStandardisedContinuousInterceptIsNotStandardisedDiscreteContinuousIntercept,
+    /// Driver p. 16 `asymCINTstd` was requested with a
+    /// non-positive within-subject variance. Footnote 4
+    /// standardisation of the 2017-era `asymCINT` vector
+    /// requires strictly positive `asymDIFFUSION`.
+    StandardisedAsymptoticContinuousInterceptRequiresPositiveWithinSubjectVariance,
+    /// Driver Table 2 unstandardised `asymCINT` `-κ / a` was
+    /// treated as `asymCINTstd`. Unstandardised asymptotic
+    /// intercept is defined for a zero process; standardised
+    /// `asymCINT` is not.
+    UnstandardisedAsymptoticContinuousInterceptIsNotStandardisedAsymptoticContinuousIntercept,
+    /// Driver p. 16 `CINTstd` analog `κ / √p` was treated as
+    /// `asymCINTstd`. The continuous intercept standardisation
+    /// is not the standardised total intercept change.
+    StandardisedContinuousInterceptIsNotStandardisedAsymptoticContinuousIntercept,
+    /// Driver p. 16 `discreteCINTstd` was treated as
+    /// `asymCINTstd`. A finite event interval is not the
+    /// `Δt → ∞` intercept change.
+    StandardisedDiscreteContinuousInterceptIsNotStandardisedAsymptoticContinuousIntercept,
 }
 
 impl fmt::Display for PsychometricError {
@@ -1832,6 +1850,18 @@ impl fmt::Display for PsychometricError {
             Self::AsymptoticStandardisedContinuousInterceptIsNotStandardisedDiscreteContinuousIntercept => {
                 "asymptotic standardised continuous intercept is not standardised discrete continuous intercept"
             }
+            Self::StandardisedAsymptoticContinuousInterceptRequiresPositiveWithinSubjectVariance => {
+                "standardised asymptotic continuous intercept requires strictly positive within-subject variance"
+            }
+            Self::UnstandardisedAsymptoticContinuousInterceptIsNotStandardisedAsymptoticContinuousIntercept => {
+                "unstandardised asymptotic continuous intercept is not standardised asymptotic continuous intercept"
+            }
+            Self::StandardisedContinuousInterceptIsNotStandardisedAsymptoticContinuousIntercept => {
+                "standardised continuous intercept is not standardised asymptotic continuous intercept"
+            }
+            Self::StandardisedDiscreteContinuousInterceptIsNotStandardisedAsymptoticContinuousIntercept => {
+                "standardised discrete continuous intercept is not standardised asymptotic continuous intercept"
+            }
         };
         formatter.write_str(message)
     }
@@ -3163,4 +3193,28 @@ mod tests {
             "asymptotic standardised continuous intercept is not standardised discrete continuous intercept"
         );
     }
+
+    #[test]
+    fn standardised_asymptotic_continuous_intercept_boundary_messages_are_stable() {
+        assert_eq!(
+            PsychometricError::StandardisedAsymptoticContinuousInterceptRequiresPositiveWithinSubjectVariance
+                .to_string(),
+            "standardised asymptotic continuous intercept requires strictly positive within-subject variance"
+        );
+        assert_eq!(
+            PsychometricError::UnstandardisedAsymptoticContinuousInterceptIsNotStandardisedAsymptoticContinuousIntercept
+                .to_string(),
+            "unstandardised asymptotic continuous intercept is not standardised asymptotic continuous intercept"
+        );
+        assert_eq!(
+            PsychometricError::StandardisedContinuousInterceptIsNotStandardisedAsymptoticContinuousIntercept
+                .to_string(),
+            "standardised continuous intercept is not standardised asymptotic continuous intercept"
+        );
+        assert_eq!(
+            PsychometricError::StandardisedDiscreteContinuousInterceptIsNotStandardisedAsymptoticContinuousIntercept
+                .to_string(),
+            "standardised discrete continuous intercept is not standardised asymptotic continuous intercept"
+        );
+    }
 }