Tools for Those Who Summarize the Evidence Base
Dear Mike and Others,
I am trying to estimate a random effects tssem for my dissertation.I have read your book and related papers. I am following the wonderful resources provided by you and your team. My goal is to perform some moderator analyses using categorical variables, after I successfully run the tssem model.
I am attaching my data, R script and the structural model. In this data and model, the tssem1 did not execute due to the positive definite problem. So, I followed your suggestions in Cheung and Hafdahl (2016), and hence tried adding the options acov = "weighted" and acov = "unweighted". This helped in successfully running the tssem1 model. But the tssem2 model produced the following error
Error in wls(Cov = pooledS, asyCov = asyCov, n = tssem1.obj$total.n, Amatrix = Amatrix, :
"Cov" is not positive definite.
Indeed, the matrix was not positive definte when I inspected. How do I work around this error? How can I find a subset of studies in my dataset that is positive definite (without loosing the data points)? Interestingly, the tssem1 worked when I ran the with the first 40 studies in this dataset (even without the acov option) .
I find the multivariate metasem to be fascinating. I want to strengthen my dissertation with this rigorous approach to metasem. So, any help in solving my issue would be great.
Thanks in advance for your help.