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