OpenMx Structural Equation Modeling

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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.

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Picture of user. paulT Joined: 11/03/2017

Empirical Underidentification with a bifactor type model

First post by new user: Can anyone give some advice on an empirical under-identification issue please? I am trying to fit the following model:

resVars <- mxPath( from=mylabels, arrows=2,
free=TRUE, values=rep(1,12),
labelatVars <- mxPath( from=c("X1","X2"), arrows=2, connect="unique.pairs",
free=c(TRUE,FALSE,TRUE), values=c(1,0,1), labels=c("varX1","cov","varX2") )

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No user picture. cjcook Joined: 05/22/2017

LISREL Simulation

Hello,

I am trying to simulate data using the endogenous variables only LISREL model as seen on page 133 of the OpenMx.pdf help documentation. I was able to simulate data from a state space model using the example in the help documentation on page 174. Now I am modifying that piece of code for a LISREL model. However I am running into an error. Below is my code.

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Picture of user. Soyoung Joined: 05/08/2017

multilevel path/structural equation models in OpenMx

Hi,

Is it possible to estimate multilevel path/structural equation models with OpenMx?
If it is possible, is there an example code for multilevel mediation (path) model?

Attached files are the example of multilevel path model using Mplus.
Source: Heck, R. H., & Thomas, S. L. (2015). An introduction to multilevel modeling techniques: MLM and SEM approaches using Mplus. Routledge.

Hope I can do the same analysis using OpenMx.

Thank you in advance.
Soyoung.

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Picture of user. iloo Joined: 05/26/2010

Optimization issues - binary with low prevalence

Hey,
I work with OpenMx using a bit different data than most others; often data comes from a full population and has quite many rows (up to 3 million). A common type of analysis is for relatives with one or more binary variables, e.g. observed disease diagnosis, where the prevalence is low, e.g. 1% to 0.05%. The complexity of the models vary from simple 2x2 covariance matrices without any definition variables to 8x8 covariance matrices with several definition variables adjusting the means/thresholds.

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No user picture. IvanVoronin Joined: 08/18/2013

Wierd estimate of mean in a simple model

Dear all,

I've met a weird issue with means running a simple model.

The data:
Cov<-matrix(
c(10,3.0,6.5,
3.0,10,6.5,
6.5,6.5,10),ncol=3,nrow=3)
library('mvtnorm')
data<-as.data.frame(rmvnorm(1000,mean=rep(100,3),sigma=Cov))
names(data)<-c('X','Y','Z')

The covariance matrix corresponds the model:
X -> Z = 0.5
Y -> Z = 0.5
X <-> Y = 3
X <-> X = 10
Y <-> Y = 10
Z <-> Z = 3.5
All means are 100

The model:
aModel<-mxModel(type='RAM',name='Phenotypic model',
manifestVars=c('X','Y','Z'),
mxPath(from=c('X','Y'),to='Z',connect='single',

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Picture of user. rabil Joined: 01/14/2010

Interpreting Output from mxTryHardOrdinal

The output below says a solution was found, but was it?

Begin fit attempt 21 of at maximum 21 tries