General SEM Discussions
pehkawn
Joined: 05/24/2020
Delta parameterization of ordinal veriables
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
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
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yaning
Joined: 04/12/2019
Doubt with compare between saturated and ACE model
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
[![Latent interaction regression model][1]][1]
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Arthur
Joined: 02/13/2020
Genetic correlation bellow -1
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
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
Some questions about the GxE model:
From Wikipedia,
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khusmann
Joined: 08/11/2019
Sample weights / complex study designs
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