Dear Lisa, There doesn't seem to be anything logically wrong with your model.
I don't have much time today to look into it, but trying different optimizers in version 2.0-0 of sem, using the correlation matrix in place of the covariance matrix, and setting the par.size parameter, I was unable to obtain an admissible solution. I also was unable using factanal() to fit an exploratory factor analysis for five factors to your data. I expect that the problem is ill-conditioned. Best, John ------------------------------------------------ John Fox Sen. William McMaster Prof. of Social Statistics Department of Sociology McMaster University Hamilton, Ontario, Canada http://socserv.mcmaster.ca/jfox/ On Tue, 8 Nov 2011 08:18:28 -0800 (PST) lisamp85 <lisamlp...@gmail.com> wrote: > Hello. > > I started using the sem package in R and after a lot of searching and trying > things I am still having difficulty. I get the following error message when > I use the sem() function: > > Warning message: > In sem.default(ram = ram, S = S, N = N, param.names = pars, var.names = > vars, : > Could not compute QR decomposition of Hessian. > Optimization probably did not converge. > > I started with a simple example using the specify.model() function, but it > is really straight forward. I uploaded my specify.model script and my data > covariance matrix here too so I wouldn't clutter this email with the entire > model (20 observed variables, 5 factors). Could this error message be from > the data itself and not from my path model? > > I have my observed variables X and my unobserved variables F. I have ONLY > exogenous latent variables (i.e. they never appear on the right side of the > single head arrow ->). I include all possible factor covariances FjFk, and > the only constraints I've made was to restrict the Factor variances to 1. > My model follows in this basic format (as you can see from my uploaded > file): > > # Factors (where I specify which observed variables load on to which > factors) > # I have only exogenous latent variables > F.i -> X.j, lamj.i, NA > . > . > . > # Observed variable variances > X.j <-> X.j, ej, NA > . > . > . > # Factor variances (I fixed all factor variances to 1) > F.i <-> F.i, NA, 1 > . > . > . > # Factor covariances (I represent all factor covariances, i.e. the upper or > lower triangle of a covariance matrix) > F.i <-> F.k, FiFk, NA > . > . > . > > Did I do something wrong here? > Here are my uploaded files: > CFA script: http://r.789695.n4.nabble.com/file/n4016569/CFA_script.txt > CFA_script.txt > Covariance matrix: > http://r.789695.n4.nabble.com/file/n4016569/covariance_matrix.RData > covariance_matrix.RData > > > Thank you so much for any and all of your help. > Lisa > > -- > View this message in context: > http://r.789695.n4.nabble.com/Help-with-SEM-package-Error-message-tp4016569p4016569.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
