[R] Questions regarding sem using hetcor() function from polycor and diagrams

[Stella Copeland]

Hello R Users,

While I have attempted to dig into the R help files and I have not 
identified the answer to these questions, I apologize in advance if my 
questions were answered in the past.  I also recognize that one of my 
questions unfortunately verges on statistical rather than code 
territory. I have two rather unrelated questions about using the sem and 
polycor packages for a relatively simple confirmatory path analysis:

(1) My data requires using the hetcor function from the polycor package, 
and I ran the sem() function using a matrix from this code:

hcor<-function(data) 
hetcor(data,std.err=FALSE,use="pairwise.complete.obs")$correlations

I believe this means I am using a correlation rather than a covariance 
matrix for the model fit statistics. I am then assuming (perhaps 
incorrectly) that the model fit and coefficient p values are reliable. 
However, I don't know if there are additional steps I should go to in 
order to report the correct standardized coefficients for my the model? 
The boot.sem() function results in identical parameter estimates but 
slightly altered standard errors. Are these boot strapped errors the 
right ones to report if I am interested in reporting standardized 
coefficients from this model? If this description sets off alarm bells 
(as in, it appears I have misunderstood the basics of the statistics 
behind the code I am using), I would appreciate constructive criticism 
regarding the correct code to use.

(2) I also searching for a way to use graphviz to create graphs with 
arrow widths corresponding to the value of the standardized coefficients 
(as in several J.B. Grace publications with data similar to my own). 
Ideally, the coefficient values would also be embedded within the arrows.

Any insight is much appreciated.

Thank you,
Stella


-- 
Stella Copeland
PhD Student
Graduate Group in Ecology
University of California, Davis