OpenSEM Forums
falkcarl
Joined: 10/29/2015
lower bounds on slopes of dichotomous and graded item response models
When doing estimation of item factor analysis models in OpenMx, I'm wondering if there's a way to override the lower boundary on the item slopes (currently 1e-6, I think) for the dichotomous and graded item response models. e.g., imagine one wants to fit a multidimensional model, perhaps w/ crossloadings, or one has reverse worded items and it is expected that some item slopes will go negative. I believe these bounds may be set in the rpf package as rpf.ParamInfo returns this lower bound for the rpf.drm and rpf.grm item models.
Aurina
Joined: 01/05/2016
Residuals in ACE model with covariates
Hello all,
I am really new in twin modeling as well as in R, therefore I would be very grateful if someone could advise me on a few issues regarding the script.
I am trying to run an ACE model with covariates (sex and age) on some twin height data. It would be very helpful to know whether the script (attached: test_height.R) does not have any major flaws and does what is expected of it. And one more thing, I would like to plot the residuals after performing the regression on the data. Could you please help me to find the most straight forward way to do that?
- Read more about Residuals in ACE model with covariates
- 6 comments
- Log in or register to post comments
yassinebha
Joined: 01/02/2016
how to model Twins and non twins siblings
Anyone knows how to use OpenMx for twins study including non twins siblings, like family model?
Thanks
- Read more about how to model Twins and non twins siblings
- 5 comments
- Log in or register to post comments
jbizzle09
Joined: 10/02/2015
Bivariate model for ordinal and continuous data
I would like to run a bivariate model for an ordinal variable and a continuous variable. The ordinal variable was measured in childhood and the continuous variable was measured in adulthood - therefore it makes sense that I should use a Cholesky decomposition testing whether the ACE influences on the ordinal (childhood) variable also influence the continuous (adulthood) variable. However in a liability threshold model for continuous and ordinal data, the ordinal variable should go last.
tbates
Joined: 07/31/2009
Moderation models: Moderators as interaction terms, and model drawing
This link depicts a simple manifest-variable moderation as shown in the images below (along with Mplus code). The path diagrams don't inclde residuals, or, for instance moderator <-> predictor covariance, nor how covariance is implement (if at all) between XW and the main effects X and W.
A couple of questions.
- Does anyone have a pointer to path diagrams that are complete (i.e with residuals and covariances?)
- Using RAM, can the moderation be implemented as an algebra on the X->Y path?
Cindy.s
Joined: 07/04/2015
Logistic regression correcting for twin data
Hi OpenMX community!
I would like to run a simple logistic regression model, but with a classical twin dataset, correcting for the fact that they are twins and their zygosity MZ or DZ. Is there a way for such analysis using OpenMx?
Thanks!
- Read more about Logistic regression correcting for twin data
- 2 comments
- Log in or register to post comments
Rolandgem
Joined: 10/24/2015
Univariate Binary Model with multiple covariates that are binary, categorical, and continuous.
This is my first attempt at binary univariate models with multiple covariates. When i fit the saturated model I get the following error which I am not sure what it actually means:
Error in runHelper(model, frontendStart, intervals, silent, suppressWarnings, :
MxComputeConfidenceInterval: reference fit is not finite
My guess is that it has something to do with the values or bounds?
What are some guidelines for choosing values when you have binary variables (as well as a mix of binary and continuous covariates)?
Yuan
Joined: 02/13/2015
estimate CI
Hi everyone,
I'm recently learning the univariate twin analysis. According to the documents, I got the a2, c2, and e2. How could I estimate the confidence intervals for each value? Thanks.
- Read more about estimate CI
- 4 comments
- Log in or register to post comments
newbie
Joined: 09/07/2015
Missing data in longitudinal study
Hello all,
- Read more about Missing data in longitudinal study
- 3 comments
- Log in or register to post comments
YiTan
Joined: 10/08/2014
Equating covariances as a test for sex-limitation effects?
Hi all,
I have a question about sex-limitation model testing. I came across an article which mentioned the following (http://www.ncbi.nlm.nih.gov/pubmed/15685427) :