Confirmatory Factor Analysis and Measurement Models

Hello,

Hi,

I am a novice R user, who is committed to learning OpenMx for structural equation modeling for my research in psychology. I have been using the reference manual as a guide for setting up the syntax for the measurement model of my analysis. I have 19 manifest variables, and 7 latent constructs, for which I would like to obtain general fit indices, parameter estimates and modification indices. I tried to run the analysis using raw data that has less than 5% missingness. The following error messages were produced:

Error: unexpected ',' in "values=c(1,1,1),"

Hi,

This is literally the first day I every used OpenMx so it is all quite new to me, maybe I am making a stupid mistake here.

I am attempting to perform a two-group CFA of one continuous factor on six ordinal predictors in OpenMx using Weighted Least Squares (WLS) estimation. I have the polychoric correlation/covariance matrices and I managed to get it working with help of:

http://openmx.psyc.virginia.edu/docs/OpenMx/latest/FactorAnalysisOrdinal_Matrix.html
http://openmx.psyc.virginia.edu/thread/530

Hello,

I took a quick look through the documentation and couldn't find anything on running multilevel CFA/EFA in openmx. Specifically, I'm interested in running a two level CFA where observations are nested within participants. I believe that Muthen (1994) reports a similar model to the one that I am interested in running. Also, is there any documentation on running multilevel EFA? I'm interested in running something similar to Vijver (2002). Thanks!

Muthén, B. O. (1994). Multilevel covariance structure analysis. Sociological Methods & Research, 22, 376-398.

Hi all,

I am a grad student at Aarhus University, Denmark. I am fairly new with SEM but have read as much literature as I could possibly get my hands on. I am working in AMOS. I have attached a picture of the AMOS setup.

I have set up a model containing 3 latent factors, each with 6 observed variables attached.

Hello! As the subject line states, I want to run a one-factor CFA with four indicators; however, when I run the model in OpenMx, I get -2 degrees of freedom. That makes sense because there are 6 correlations (given 4 indicators), and if I fix the factor variance to 1.0, I have to estimate 4 loadings and 4 error variances = 8 estimates, and we all know that 6 correlations - 8 estimates = -2 df.

I was trying to run a piece of code to measure MEBS (30 items) across gender and I got an error message which says: "Error: The job for model 'Moderated FI Model' exited abnormally with the error message: Expected covariance matrix is not positive-definite in row 0.".

I was trying to change the starting values (say, by making all of the covariances and free regressions .5) by taking suggestion posed on the forum and got the same error message. Does anyone can help on this? Thanks.

Yunfei

-------------the code ---------------
options(width=110)
library(psych)
library(OpenMx)

Hi all,
First, thanks to do this job for R, it's really needed!
I am trying to do a CFA with 6 factors (psychological self report questionnaire with 6 scales with 14 items each).
I tried to adapt the two factors models. Seeing this discussion, I changed
the starting values and got no warning message. I have a few issues though:
1. For the latent covariance and variances of the 2 factors you give the
example of values=c(1, .5,.5, 1) But how can I organize it with 6 factors? Why do we need
to specify starting values, in sem package none is needed. Is it a specificity of the program ?

I've tried running a simple CFA in OpenMx, using the tutorials and adapting an example, but the results are not what I expected. Specifically, I get no fit indices (e.g., RMSEA, chi-square, etc.). It certainly may be due to my data or my too-simplistic model or something. Any help in either (a) understanding why I get the results I do, or (b) helping me figure out how to get the results I am more accustomed to, would be greatly appreciated.

I understand that Mx could be used to handle ordinal manifest variables but I could never follow the one example script I had.

Is it possible to have ordinal manifest variables using OpenMx? I hate to ask seeing how confidence intervals have now been added (yea!) which would allow me to use OpenMx in place of Mx for a number of analyses.

I have 3 raters rating 2 eyes for each subject so that there are 6 measurements for each subject, something like:

subject od.1 od.2 od.3 os.1 os.2 os.3
1 X X X X X X
2 X X X X X X