Are lavaan::lavInspect(fit, "converged") and lavaan::lavTech(fit, "post.check") redundant?

[Michael Truong]

Hello,

I was just curious about something because I couldn't get a quick answer on Google and because I figured that others probably would want to be able to see this on Google quickly.

Is it true that lavaan::lavInspect(fit, "converged") and lavaan::lavTech(fit, "post.check") are non-redundant to each other? 

Looking at the documentation, https://cran.r-universe.dev/lavaan/doc/manual.html, the former seems to be about whether the optimizer has stopped, whereas the latter is for whether the parameter estimates is admissible. 

I'm just re-stating the documentation, but intuitively, I would've expected one function that covers everything. I also know that at least a few people would've mistakenly assumed that checking lavaan::lavInspect(fit, "converged") is sufficient during simulation studies, but I'm guessing that is probably not true...

Michael

[Yves Rosseel]

They are very different:

- "converged" is indeed about the optimizer only; most algorithms in
lavaan are iterative (using the nlminb() function) and the optimizer may
simply not converge, implying that it did not find a (reasonable) solution

- "post.check" is only relevant if the model converged; this is a check
to see if the estimated parameter values are all 'admissible' (i.e., no
negative variances, all covariance matrices positive-definite); this is
a very different type of information; not everyone wants to 'exclude'
improper (but converged) solutions in a simulation study, because not
everybody feels that, say, a tiny negative variance is problematic (in
particular when the sample size is small)

Yves.

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