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Exponential decay growth model with E... |
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Trying to fit exponential decay growth model with estimator = bayes, can't get around this problem: *** ERROR For analysis with ESTIMATOR=BAYES, NEW parameters must appear on the left-hand side in at least one MODEL CONSTRAINT equation. No equation found containing parameter on the left-hand side: ERATE Is there a work-around? MODEL: INIT BY ANX1@1; INIT BY ANX2-ANX5* (L12-L15); RATE BY ANX1@0; RATE BY ANX2-ANX5* (L22-L25); ASYMP BY ANX1@0; ASYMP BY ANX2-ANX5* (L32-L35); !Name means of latent vars. [ASYMP] (AS); [INIT] (IN); [RATE@0]; MODEL CONSTRAINT: !Create a new var equals for mean of latent rate of change. NEW(ERATE); L12=exp(-1*Erate); L13=exp(-2*Erate); L14=exp(-3*Erate); L15=exp(-4*Erate); L22=(AS - IN)*1*exp(-1*Erate); L23=(AS - IN)*2*exp(-2*Erate); L24=(AS - IN)*3*exp(-3*Erate); L25=(AS - IN)*4*exp(-4*Erate); L32=1-exp(-1*Erate); L33=1-exp(-2*Erate); L34=1-exp(-3*Erate); L35=1-exp(-4*Erate); |
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Mplus Bayes does not currently accept restrictions on parameters like here, only new, free parameters (so LHS). Don't know about a work-around except to try ML (with BS). |
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Ah... that's a shame. I'll need to stick with ML then. The issue that I'm getting with this approach (and hence the motivation for trying Bayesian estimation) is that I keep getting a negative variance estimate for RATE (and it's not very close to zero, so no quick 'fixing to close to 0' type solution seems correct!). I've tried fixing it to be > 0 but then I get a correlation > 1 popping up... |
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Could you use exp(erate) instead of erate to keep it non-negative? With ML, that is. |
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