Structural equation modeling in R(lavaan,sem)

Daer all,
I have a question concerning longitudinal data:
When we have a longitudinal data and we have to do sem analysis there is in the package lavaan some functions,options in this package that help to do this or we can treat these data like non longitudinal data

No, and (qualified) no.

1. There are (AFAIK) no options, functions that are specific to
longitudinal data.

2. You don't treat these data as non-longitudinal data, you add
parameters that are appropriate though.  For example, look at the
model shown on http://lavaan.ugent.be.  dem60 and dem65 are two
measures of the same construct at different timepoints, so there are
correlations over time for each pair of measured variables that are
measures of that construct - i.e. y1 ~~ y5

3. You would get much better answers on the SEM mailing list - semnet.
You can join it here: http://www2.gsu.edu/~mkteer/semnet.html#Joining.

Jeremy

Jeremy Miles
Psychology Research Methods Wiki: www.researchmethodsinpsychology.com

Daer all, I have a question concerning longitudinal data: When we
have a longitudinal data and we have to do sem analysis there is in
the package lavaan some functions,options in this package that help
to do this or we can treat these data like non longitudinal data

The function 'growth' (in the lavaan package) can be used for (standard) 
growth modeling. Good material about growth modeling (using Mplus) can 
be found here:

http://statistics.ats.ucla.edu/stat/mplus/seminars/gm/default.htm

Next, you can read how to do growth modeling with lavaan by reading 
section 7 in the lavaan intro, which you can download from the 
documentation section on the lavaan website (http://lavaan.org).

Yves.

Yves Rosseel -- http://www.da.ugent.be
Department of Data Analysis, Ghent University
Henri Dunantlaan 1, B-9000 Gent, Belgium

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Thanks you for your response
For lavaan package can i have more information about this example you have applied in the section 7
the meanings  of The variables (c1,c2,c3,c4, i ,s ,x1,x2)
I think i have need more information to learn  more about how  able to apply growth model  in my data (longitudianl data)

In the example, c1-c4 are time-varying covariates, i and s are the 
random intercept and slope respectively, and x1 and x2 are two exogenous 
covariates influencing the intercept and slope.

Please note: the lavaanIntroduction document is hardly useful to _learn_ 
about growth models (or any SEM model for that matter). It only explains 
how to fit them using the lavaan package. To learn about growth models, 
you may want to read any one of the books below:

Latent Curve Models: A Structural Equation Perspective (Wiley Series in 
Probability and Statistics) by Kenneth A. Bollen and Patrick J. Curran 
(Hardcover - Dec 23, 2005)

Latent Growth Curve Modeling (Quantitative Applications in the Social 
Sciences) by Dr. Kristopher J. Preacher, Aaron Lee Wichman, Robert 
Charles MacCallum and Dr. Nancy E. Briggs (Paperback - Jun 27, 2008)

An Introduction to Latent Variable Growth Curve Modeling: Concepts, 
Issues, and Applications (Quantitative Methodology) (Quantitative 
Methodology Series) by Terry E. Duncan, Susan C. Duncan and Lisa A. 
Strycker (Paperback - May 23, 2006)

Yves.

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