[R] R SEM package

[Anthony Dick]

Hi John-

Thanks for responding so quickly. Love the package by the way.

I am using R sem to model fMRI data, and I want to compare models 
between conditions (i.e., to see if there is a significant difference 
between specific path coefficients of two models). I believe this 
amounts to what is commonly referred to as a multi-group analysis, where 
two models are run simultaneously, allowing some coefficients to vary 
while others are maintained. The procedure is described briefly in the 
Appendix of: Pugesek & Tomer (1996). Evolutionary Ecology, 10, 387-404.

I am not sure if anova() does what I want it to.

Anthony

John Fox wrote:
> Dear Anthony,
>
> I'm not sure what you mean by a "stacked model comparison." If you mean a
> model fit to multiple groups, then the answer is no. If you mean comparison
> of nested models, then anova() can be used to get a LR test. See ?anova.sem.
>
> I hope this helps,
>  John
>
> ------------------------------
> John Fox, Professor
> Department of Sociology
> McMaster University
> Hamilton, Ontario, Canada
> web: socserv.mcmaster.ca/jfox
>
>
>   
>> -----Original Message-----
>> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
>>     
> On
>   
>> Behalf Of Anthony Dick
>> Sent: January-06-09 2:56 PM
>> To: r-help at r-project.org
>> Subject: [R] R SEM package
>>
>> Does anyone know if the sem package in R can implement a stacked model
>> comparison, for example as in LISREL or AMOS?
>>
>> Thanks,
>>
>> Anthony
>>
>> --
>> Anthony Steven Dick, Ph.D.
>> Post-Doctoral Fellow
>> Human Neuroscience Laboratory
>> Department of Neurology
>> The University of Chicago
>> 5841 S. Maryland Ave. MC-2030
>> Chicago, IL 60637
>> Phone: (773)-834-7770
>> Email: adick at uchicago.edu
>> Web: http://home.uchicago.edu/~adick/
>>
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>>     
>
>
>   


-- 
Anthony Steven Dick, Ph.D.
Post-Doctoral Fellow
Human Neuroscience Laboratory
Department of Neurology
The University of Chicago
5841 S. Maryland Ave. MC-2030
Chicago, IL 60637
Phone: (773)-834-7770
Email: adick at uchicago.edu
Web: http://home.uchicago.edu/~adick/