General SEM Discussions
pehkawn
Joined: 05/24/2020
Delta parameterization of ordinal veriables
There are several model parameters available for an ordinal variable that can set the
ordinal variable’s scale and location. The two most common seem to be *delta* parameterization (fixing total means and total variances to 0 and 1) and *theta* parameterization (fixing residual means and residual variances to 0 and 1).
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Benny
Joined: 05/15/2020
mxAlgebra input
Hello,
for a SEM model I have calculated the expected covariance matrix using the symbolic linear algebra functionalities of the `Ryacas` package. To use the expected covariance matrix to calculate some second order statistics, I'm wondering whether the `mxAlgebra` function accepts some sort of R objects/expressions? Or does it only accept the "raw" names of the `mxMatrix` objects? I'm grateful for any hint on the topic.
Thanks!
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hpar
Joined: 03/30/2021
using t-values as input data in SEM
Hi all,
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yaning
Joined: 04/12/2019
Doubt with compare between saturated and ACE model
Hello, everyone:
I'm running a bivariate twin model to estimate the correlation between a continuous variable (BMI) and a binary variable (CHD).
I have two questions:
First, i fund the means between MZ and DZ twins are different, do i need to constrain them with the same value in the ACE model;
Second, the p value between the saturated model and ACE model was＜0.05, what does this mean. Can i use ACE model to estimate the genetic and environmental correlation.
Thank you so much for your help.
pehkawn
Joined: 05/24/2020
Latent variable interactions/moderation
I am currently trying to create a latent interaction regression model in OpenMx where I have four latent variables (C, H, T, S) that predicts a fifth latent variable (A). In addition, interaction effects between the main latent predictor C, and H, T, and S should be included.
[![Latent interaction regression model][1]][1]
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Arthur
Joined: 02/13/2020
Genetic correlation bellow -1
Dear OpenMx team and users,
I am running an AE multivariate twin model with a sample of 21 DZ twin pairs and 50 MZ twin pairs on 4 variables. The Genetic correlation between two of these variables is -1.10.
So my obvious question is; what possible reasons could explain this correlation bellow -1? Could it be related to the absence of "C" or "D" in the model? Or could it be related to the sample size?
Many thanks,
Arthur
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ReddyM
Joined: 10/02/2019
mxbootstrap
Hi,
Is there a way to write out to console the number of replication being computed? Just because for some models it can take a lot of time to bootstrap, and this way would be easier to know when it will be finished.
Thanks in advance, ReddyM
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yaning
Joined: 04/12/2019
questions about the GxE model
Hi, everyone
Some questions about the GxE model:
From Wikipedia,
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khusmann
Joined: 08/11/2019
Sample weights / complex study designs
Hi all,
I'm wondering what is the proper way to do sample weights in OpenMx >2.0? I found this [old thread](https://openmx.ssri.psu.edu/thread/3661) with an example that uses `mxFIMLObjective`, but `mxFIMLObjective` looks to be deprecated. Any help with a working example would be much appreciated!
Also, this way of doing weights by nesting mxModels seems pretty cumbersome -- is there an updated interface or a way to "tack on" weights to an existing model definition? (Ideally I'd like a way for models to be easy to run with and without weights).
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Julia
Joined: 03/29/2012