New poster here, and new-ish user to twin analyses. I am trying to run an ACE model that I believe is called "scalar sex limited" -- I want to allow the total variance to differ across sex, but I want to constrain the A, C, and E to be the same so that I am reporting just one heritability estimate. Here are the key parts of my syntax:
twinACEModel <- mxModel("twinACE", mxModel("ACE", # ace path coefficients for males and females mxMatrix("Lower", nrow=nv, ncol=nv, free=TRUE, values=0.2, label="am11", name="am"), mxMatrix("Lower", nrow=nv, ncol=nv, free=TRUE, values=0.3, label="cm11", name="cm"), mxMatrix("Lower", nrow=nv, ncol=nv, free=TRUE, values=0.5, label="em11", name="em"), mxMatrix("Lower", nrow=nv, ncol=nv, free=TRUE, values=0.2, label="am11", name="af"), mxMatrix("Lower", nrow=nv, ncol=nv, free=TRUE, values=0.3, label="cm11", name="cf"), mxMatrix("Lower", nrow=nv, ncol=nv, free=TRUE, values=0.5, label="em11", name="ef"), mxMatrix(type="Diag", 2, 2, labels=rep("k",2), free=TRUE, values=1, name="scalar"), # ACE variance components for males and females mxAlgebra(am %*% t(am), name="Am"), mxAlgebra(cm %*% t(cm), name="Cm"), mxAlgebra(em %*% t(em), name="Em"), mxAlgebra(af %*% t(af), name="Af"), mxAlgebra(cf %*% t(cf), name="Cf"), mxAlgebra(ef %*% t(ef), name="Ef"),
I'm correcting for age and sex.
mxModel("DZm", mxData(observed=dzData , type="raw"), mxMatrix( type="Full", nrow=1, ncol=2, free=FALSE, label=c("data.ageT1", "data.ageT2"), name="obs_age" ), mxMatrix( type="Full", nrow=1, ncol=2, free=FALSE, label=c("data.sexT1", "data.sexT2"), name="obs_sex" ), mxAlgebra( expression= ACE.expMean + ACE.betasex %x% obs_sex + ACE.betaage %x% obs_age, name="expMean"), mxFIMLObjective(covariance="ACE.expCovDZm", means="ACE.expMean", dimnames=selVars) ),
I'm trying to figure out how to get the twin correlations. I've seen some other posts where people get the twin correlations through saturated models -- is there something wrong with trying to grab them from my ACE model? E.g., just asking for confidence intervals for expCovDZm, expCovDZf, expCovMZm, and expCovMZf? (If my model has worked right, I believe expCovDZm should = expCovDZf, and same for MZ).
Thanks.