[R] path analysis help

[John Fox]

Dear Jinsong,

This model is grossly underidentified because there are no exogenous
variables in it. Your inability to estimate the model isn't a software
issue.

Best,
 John

-----------------------------------------------
John Fox
Senator McMaster Professor of Social Statistics
Department of Sociology
McMaster University
Hamilton, Ontario, Canada



> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
> On Behalf Of Jinsong Zhao
> Sent: Thursday, August 30, 2012 10:47 AM
> To: r-help at r-project.org
> Subject: [R] path analysis help
> 
> Hi there,
> 
> I searched R-help list with "path analysis" as keyword, and learn that
> sem package can do it. However, I don't figure out a way to construct
> the model for the path diagram as Fig. 1. in Huang et al. (2002)[1].
> 
> I try the following code:
> 
> huang.cor <- readMoments(diag=FALSE, names=c('x1', 'x2', 'x3', 'y'))
> 0.76
> 0.91 0.72
> 0.94 0.77 0.83
> 
> huang.mod <- specifyModel()
> x1 -> y, p1
> x2 -> y, p2
> x3 -> y, p3
> x1 -> x2, p12
> x2 -> x1, p21
> x2 -> x3, p23
> x3 -> x2, p32
> x1 -> x3, p13
> x3 -> x1, p31
> 
> huang.sem <- sem(huang.mod, huang.cor, 100)# 100 is arbitarious.
> 
> It give the error message:
> 
> Error in sem.default(ram, S = S, N = N, raw = raw, data = data,
> param.names = pars,  :
>    The model has negative degrees of freedom = -3
> 
> I don't know why.
> 
> I hope to get direct effect, indirect effect and total effects for every
> variable. However, I don't figure out how to do with sem package. It
> there any other package that can do it?
> 
> Any suggestion or hint will be greatly appreciated.
> 
> Regards,
> Jinsong
> 
> 
> [1] Huang, B., Thornhill, N., Shah, S. and Shook, D. (2002). Path
> analysis for process troubleshooting. Proceedings of Advanced Control of
> Industrial Processes, Kumamoto, Japan, 10-12 June, 149-154.
> url: http://eprints.ucl.ac.uk/494/1/HuangEtAl_AdConIP_2002.pdf
> 
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