Dear Amarnath Bose, S is the observed-variables covariance or moment matrix and thus doesn't really have to do with the model that you're fitting, nor with the sem software per se; rather, S is computed directly from the data.
It's not possible without the data to know why S is numerically singular. The message you quote suggests three reasons, but these aren't exhaustive. Investigating the eigenstructure or SVD of S or the data matrix might help -- e.g., through a principal components analysis. I hope this helps, John ----------------------------------------------- John Fox Senator McMaster Professor of Social Statistics Department of Sociology McMaster University Hamilton, Ontario, Canada > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-bounces@r- > project.org] On Behalf Of Amarnath Bose > Sent: Tuesday, April 09, 2013 8:22 AM > To: r-help@r-project.org > Subject: [R] sem: S is numerically singular: expect problems > > Dear Users, > > I am a new user of the sem package. > I have a model that is being flagged by sem as "S is numerically > singular: > expect problems" > > I have checked John Fox's response to a similar problem. Obviously the > variance-covariance matrix is singular, but none of the possible > reasons > seems to hold in my case. > > Any leads how I could get the model to work? > > from Prof. John Fox > > That seems to me a reasonably informative error message: The > observed-variable covariance matrix is singular. This could happen, > e.g., if > two observed variables are perfectly correlated, if an observed > variable had > 0 variance, or if there were more observed variables than observations. > > Thanks > > > -- > > > *Amarnath Bose* > * **Associate Professor * > *Decision Sciences Department* > *Birla Institute of Management Technology > * > Tel: +91 120 2323001 - 10 Ext.: 398 > Cell: +91 9873179813 > > [[alternative HTML version deleted]] > > ______________________________________________ > 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.
