At 08:51 02/08/2007, Ramon Martínez Coscollà wrote:
Hi all!!
There is no need to post twice, nor to also post on allstat.
Pages 204-205 of MASS for which this software is
a support tool provides ample information on how to compare models.
I am using a proportinal odds model to study some ordered categorical
data. I am trying to predict one ordered categorical variable taking
into account only another categorical variable.
I am using polr from the R MASS library. It seems to work ok, but I'm
still getting familiar and I don't know how to assess goodness of fit.
I have this output, when using response ~ independent variable:
Residual Deviance: 327.0956
AIC: 333.0956
polr.out$df.residual
[1] 278
polr.out$edf
[1] 3
When taking out every variable... (i.e., making
formula: response ~ 1), I have:
Residual Deviance: 368.2387
AIC: 372.2387
How can I test if the model fits well? How can I check that the
independent variable effectively explains the model? Is there any
test?
Moreover, sendig summary(polr.out) I get this error:
Error in optim(start, fmin, gmin, method = BFGS, hessian = Hess, ...) :
initial value in 'vmmin' is not finite
Something to do with the optimitation procedure... but, how can I fix
it? Any help would be greatly appreciated.
Thanks.
Michael Dewey
http://www.aghmed.fsnet.co.uk
__
R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
