MASS::polr function signature is
polr(formula, data, weights, start, ..., subset, na.action,
contrasts = NULL, Hess = FALSE, model = TRUE,
method = c("logistic", "probit", "loglog", "cloglog", "cauchit"))
Read that as there are the five methods taken as a default.
Go on to the
method: logistic or probit or (complementary) log-log or cauchit (corresponding to a Cauchy latent variable)
Moving on to details
The vcov method uses the approximate Hessian: for reliable results the model matrix should be sensibly scaled with all columns having range the order of one
and other nuggets all within
Finally, a couple of text books are provided for further reference.
This answer is not a rtfm, but a reminder that closely reading the help pages can be a big help when trying to navigate. As a beginner I had an aversion to reading them. I though that
help() needed its own help page. I was abashed to find out that it does—
help(help). It was only when I began to think of
R as it presents to the user primarily as a functional language that I realized that the
help should be read as presenting the arguments for f(x) = y and the return values. Since then, I've had a much easier time.
I run through the basics of assessing
glm results here.