[R] Specifying Path Model in SEM for CFA

Rick Bilonick rab45+ at pitt.edu
Thu Aug 17 17:41:41 CEST 2006

sem() handles only equality constraints among parameters, and this model
> requires linear inequality constraints. 
> I'm aware of SEM software that handles inequality constraints, but I'm not
> aware of anything in R that will do it "out of the box." One possibility is
> to write out the likelihood (or "fitting function") for your model and
> perform a bounded optimization using optim(). It would probably be a fair
> amount of work setting up the problem.
> Finally, there are tricks that permit the imposition of general constraints
> and inequality constraints using software, like sem(), that handles only
> equality constraints. It's probably possible to do what you want using such
> a trick, but it would be awkward. See the references given in Bollen,
> Structural Equations with Latent Variables (Wiley, 1989), pp. 401-403.
> I'm sorry that I can't be of more direct help.
>  John

Thanks. I'll explore the options you mention. I would like to use R
because I need to couple this with block bootstrapping to handle time


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