[R] Can Package SEM do mean structural analysis?

John Fox jfox at mcmaster.ca
Sun May 25 21:54:36 CEST 2003

Dear Mitsuo,

The raw sums of squares and products matrix contains the sums of squares 
and sums of cross-products for the variables without subtracting the means. 
You'd add an initial column one ones to represent the means. As I said, I 
don't have time now to work out in detail whether this will allow you to 
fit models with means.


At 02:03 PM 5/25/2003 +0900, Mitsuo Igarashi wrote:
>Dear John:
>Thank you very much for your prompt explanation on the
>present possibilities of SEM.
>I am not a statistician so that I can not figure out the raw 
>sums-of-squares-and-products matrix.
>And I will do with SEM in the area without mean structural
>I appreciate your good teaching at every time.
>Mitsuo Igarashi
>mitsu5 at ruby.famille.ne.jp
>John Fox <jfox at mcmaster.ca> wrote:
> > Dear Mitsuo,
> >
> > My intention in writing the sem package was to provide a basic
> > structural-equation facility for R. I haven't made explicit provision for
> > models with means, but it might be possible to fit such models by using 
> the
> > raw sums-of-squares-and-products matrix among the observed variables
> > (perhaps divided by n) as input.  It might be necessary to make small
> > modifications to degrees of freedom, etc.
> >
> > I'm afraid that I don't have time now to figure out whether this will work
> > and, if so, precisely how to do it, but you're welcome to try. If you get
> > it to work, I'd be interested in the answer. If this approach doesn't 
> work,
> > then incorporating means would likely require major modifications to the
> > program.
> >
> > There are, by the way, several other things that dedicated
> > structural-equation software does that the sem package does not -- e.g.,
> > analysis by groups and for ordinal observed variables. I may, at some
> > point, extend the package in these directions, but I don't have plans at
> > the moment to do so.
> >
> > Good luck,
> >   John
> >
> > At 10:53 PM 5/24/2003 +0900, you wrote:
> >
> > >I am wondering whether Package SEM can do with intercepts and
> > >means in its structural analysis.
> > >
> > >If it can not calculate, how can I make a supplemental function
> > >in R?
>R-help at stat.math.ethz.ch mailing list

John Fox
Department of Sociology
McMaster University
Hamilton, Ontario, Canada L8S 4M4
email: jfox at mcmaster.ca
phone: 905-525-9140x23604
web: www.socsci.mcmaster.ca/jfox

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