OpenMx Structural Equation Modeling

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Picture of user. Mike Cheung Joined: 10/08/2009

Fixing the parameter estimates at the starting values

Hi,

I want to fit a model by using the starting values as the parameter estimates. This can quickly be done by treating them as fixed parameters. However, I also want to get some standard errors on these estimates though the starting values may not be the optimal solution.

I can fix the starting values as the estimates with `mxRun(my.model, useOptimizer = FALSE)`. But it does not provide any standard errors. Attached is an example. Any suggestions? Thanks in advance.

Mike

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No user picture. Andre Achim Joined: 02/10/2021
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No user picture. jpritsker Joined: 09/27/2020

How does OpenMx handle missing data with WLS?

I might be missing something obvious, but as far as I can tell, this isn't explicated anywhere. How does OpenMx deal with missing data for WLS? Is it listwise/pairwise or is the polychoric covariance matrix computed using FIML?
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No user picture. Jannik Joined: 10/01/2018
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Picture of user. Mike Cheung Joined: 10/08/2009

CIs on mxAlgebra

Hi, all.

I have a mxAlgebra of a parameter multiplied by a constant, say new_x = 2*x. When I construct an LBCI on both x and new_x, I expect that the CIs on new_x are the same as the CIs on x multiplied by 2. It turns out that they are not exactly the same (see the "diff" in the following output). When the constants are larger, say 5 or 10, the CIs on the new_x even become NA.

Any ideas why this happens? Thanks.


## Multiplied by 2

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Picture of user. Mike Cheung Joined: 10/08/2009

CFA with categorical variables

Hi all,

I am fitting some CFA models with all categorical variables with FIML. The information matrix is often not positive definite when the number of variables is larger than 4 or above. Attached are some examples.

Any suggestions to improve its stability? Thanks in advance.

Best,
Mike

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No user picture. blazej Joined: 11/20/2018

Help in translating a longitudinal path model to OpenMx SEM syntax

Greeting everyone!

As I'm new to SEM (in general) and OpenMx I would like to ask you for some help in specifying the model in question properly.

I'm trying to reproduce results for a 3 time points path model where specific indirect effects where of interest. The original model was depicted as in attached image.

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No user picture. blazej Joined: 11/20/2018

Looking for help with including a moderator to a path model

Greetings,
this is my 1st post, so please forgive me if this is offtopic.

In sort of new to SEM / modelling in general. So far I managed to make some sense of lavaan() syntax in R, to run a path model like this (file attached).

Before introducing the W moderator (continuous) this model was specified (in lavaan) as:

model <- '
X1 ~~ X2
A ~ X1 + X2
Y ~ A'

All variables are observed and continuous.