The reason I was working with a correlation matrix is because I wanted
to calculate polychoric correlations first before submitting it to the
actual sem command. I was unsure whether R would use polychoric
correlations when indicating which of the variables are ordered. A final
question on the sample.cov=hetcor command. Does this not assume it is a
sample variance-covariance rather than a correlation matrix (as
calculated using the polycor package)?
Yes. Sample.cov should always be a covariance matrix, not a correlation
matrix. It is pretty useless for categorical data.
I also tried using the command (thanks for the tip!)
sem.cdu= sem(cdu, data=germany2009, ordered=c("cdupid", "MERKELLIKE",
"CDULIKE", "MERKELPROX", "CDUPROX"))
but I always get the error result:
semcdu=sem(cdu, data=germany2009, ordered=c("cdupid", "MERKELLIKE",
"CDULIKE", "MERKELPROX", "CDUPROX"), fixed.x=F)
Error in tmp[cbind(REP$row[idx], REP$col[idx])] <- partable$free[idx] :
NAs are not allowed in subscripted assignments
It looks like you have some issues with your model specification. Could
you remove all '~~' statements and try again?
If the problem remains, please send me your R script, and a snippet of
the data (just enough to replicate the error).
Yves.
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