[R] sem package and growth curves

[Daniel Nordlund]

I have been working through the book "Applied longitudinal data analysis: modeling change and event occurrence" by Judith D. Singer and John B. Willett.  I have been working examples using SAS and also using it as an opportunity for learning to use R for statistical analysis.

I ran into some difficulties in chapter 8 which deals with using structural equation modeling.  I have tried to use the sem package to replicate the problem solutions in chapter 8.  I am more familiar with RAM specifications than I am with structural equations (though I am a novice at both).  The solutions I have tried seem to be very sensitive to starting values (especially with more complex models).  I don't know if this is just my lack of knowledge in this area, or something else.

Has anyone worked out solutions to the Singer and Willett examples for Chapter 8 that they would be willing to share?  I would also be interested in other simple examples using sem and RAM specifications.  If anyone is interested, I would also be willing to share the R code I have written for other chapters in the Singer and Willett book.

Thanks,

Dan

Daniel Nordlund
Bothell, WA USA