[R] additive proportional odds model in R

[David Winsemius]

On Oct 7, 2015, at 3:33 AM, Neverstop wrote:

> Hi all!
> I'm looking for a way to fit an additive proportional odds model in R since
> I need to analyse ordinal data. 
> The polr() function of the MASS package of R allows only to fit a linear
> proportional odds model so I can't use it. 

Can you explain the additional requirements you understand for your request. The polr function is additive on the log-odds scale.

> The gam() function of the gam package of R allows to fit additive models and
> generalized additive models. This package uses smoothing splines and loess
> as smoothers. I've read the documentation and it doesn't seem to be possible
> to fit an additive proportional odds model in R.      

Are you looking for an identity link with binomial errors? 

> Do you know which function should I use?

I doubt that it would allow a identity link, but the `lrm` function in `pkg:rms` is also used for ordinal proportional odds models. It supports several spline representations of functional form.


> Thank you in advance.
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David Winsemius
Alameda, CA, USA