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No user picture. Veronica_echo Joined: 02/23/2018

Question about estimates of growth models with TICs

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Longitudinal SEM and Latent Growth Curves

Hi everyone,

I am using OpenMx to fit a growth model with 2 continuous TICs. The results looked well; however, I noticed that the biases of path coefficients of the 2nd TIC were systematically larger than those of the 1st TIC in simulation studies. I am not sure if such patterns resulted from data generation, or from model misspecification, or from optimizer I used (the default one). I am attaching the script for one replication and the path diagram (with 6 repeated measures) of the model, any advice would be appreciated.

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No user picture. Mirch Joined: 10/26/2018

Adding covariates to Cholesky script

Forums
Behavioral Genetics Models

Hi there, I am a new PhD student working on a project with twins for the first time. I've been provided with some older scripts from past students and some example code from a twin analysis workshop in Queensland that I haven't been able to attend yet (which I believe was run by Sarah Medland).

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No user picture. George Richardson Joined: 10/18/2018

Sex Limitation Model Question

Forums
Behavioral Genetics Models

Hi,
I attended the Boulder workshop a couple years ago and am now trying my hand at sex limitation modeling. Currently, I am working on a same-sex twin pair sex limitation model for liability to alcohol use disorder. I've found measurement invariance and A and C are invariant. C was non-sig. and is constrained to zero. The AUD factor intercept is invariant. Can I interpret the sex difference in the AUD means in terms of greater genetic risk for AUD in the males?

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No user picture. Aurina Joined: 01/05/2016

ACE including non-twin siblings

Forums
Behavioral Genetics Models

Dear all,

I'm trying to adapt ACE heritability model to include both twins and their non-twin siblings. The data used for the analysis are imaging-derived phenotypes from the human connectome project (HCP) which includes both MZ and DZ twin pairs as well as their non-twin siblings for a subset of twins. Would be really helpful if anyone could answer a few questions.

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No user picture. cdmcdermott221 Joined: 10/09/2018

Multilevel, longitudinal model (3-level model)

Forums
Mixed Effects and Nested Models

Hello all,

I know similar questions have been posted here but I'm still unable to figure out the code for my model, as I am super new to OpenMx and structural equation modeling in general. I have intervention data collected at three time-points on children nested within schools. I would like to look at the effect of the intervention over time for the children, but taking the clustering from the schools into account. I'm trying to get my structural equation model to match this mixed model from the nlme package:

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No user picture. Jannik Joined: 10/01/2018

Errors when implementing FML function

Forums
Fit Functions

Hello,
I’m trying to implement a slightly changed Maximum Likelihood function using mxFitfunctionR and ran into some problems that I wasn’t able to solve. Here is a short version of my current attempt at implementing a covariance-based FML function without any changes:

simple_FML <- function(model, state) {
obsCov <- model$data$observed# observed covariance
nmanif <- ncol(obsCov) # number of observed variables

Sigma_try_out <- try(mxGetExpected(model,"covariance")) # expected covariance matrix

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No user picture. sealx017 Joined: 08/17/2018

Multivariate cholesky model

Forums
Behavioral Genetics Models

Hi,

I have a dataset of twins on 4 time-points. I can fit the Multivariate cholesky decompositon model with ACE components. It considers unstrcutured covariance matrices for A, C and E component. I was wondering if its possible to restrict it to a special structure? Like, say compound symmetric or AR1.

Thanks

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No user picture. Cuttlefish Joined: 09/12/2018

Different age (covariate) for siblings

Forums
Behavioral Genetics Models

Dear all,
I’m working on the bivariate ACE model from 2016 Boulder workshop from Hermione Maes ‘twoSATja’ and ‘twoACEja’ (http://ibg.colorado.edu/cdrom2016/maes/UnivariateAnalysis/scriptsOpenMx.shtml). I use questionnaire data and some participants filled this out one or two years later than their twin siblings, this means that some siblings differ in age. How do I adjust the model to allow different ages between twins? I keep running into problems with non-conforming arrays…

Below the parts of the script that I have trouble adapting:

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No user picture. massimiliano.orri Joined: 06/11/2018

Latent Growth Model and distal outcome

Forums
Behavioral Genetics Models

Hi,
I would like to fit the twin model in the enclosed figure, but I am not sure if this is feasible.
Can someone help me understanding if the model is identified?
In case, are there any exemples of R code for this model?
Thanks a lot
M

Posted on
No user picture. ethibodeau Joined: 05/16/2018

ACE decomposition of growth factors code

Forums
Longitudinal SEM and Latent Growth Curves

Does anyone have example path specification code to run a basic linear growth model where the slope and intercept factors are decomposed into ACE based on twin data? Thanks!

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